CCJ*_*CCJ 9 java android garbage-collection
我一直在寻找一些时间用于描述Dalvik VM垃圾收集器架构的详细设计文档,但是没有发现太多.考虑到GC运行的性能影响,我真的希望更好地理解5个具体问题:1.究竟是什么触发了Android中的GC？我见过的其他VM实现通常允许在GC收到运行信号之前将一定比例的系统内存分配给应用程序.然而,扫描以下LogCat似乎表明Dalvik GC至少部分运行 -
12-14 11:34:57.753: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 735 objects / 54272 bytes
in 90ms
12-14 11:34:57.893: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 256 objects / 12240 bytes
in 61ms
12-14 11:34:57.943: I/jPCT-AE(279): Loading Texture...
12-14 11:34:57.993: D/dalvikvm(279): GC_FOR_MALLOC freed 65 objects / 2840 bytes in
52ms
12-14 11:34:58.013: I/dalvikvm-heap(279): Grow heap (frag case) to 5.039MB for
1048592-byte allocation
12-14 11:34:58.073: D/dalvikvm(279): GC_FOR_MALLOC freed 1 objects / 40 bytes in 59ms
12-14 11:34:58.243: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 11 objects / 432 bytes in
55ms
12-14 11:34:58.283: I/jPCT-AE(279): Loading Texture...
12-14 11:34:58.333: D/dalvikvm(279): GC_FOR_MALLOC freed 10 objects / 416 bytes in 46ms
12-14 11:34:58.344: I/dalvikvm-heap(279): Grow heap (frag case) to 6.040MB for
1048592-byte allocation
12-14 11:34:58.423: D/dalvikvm(279): GC_FOR_MALLOC freed 2 objects / 80 bytes in 75ms
12-14 11:34:58.563: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 10 objects / 384 bytes in
47ms
12-14 11:34:58.603: I/jPCT-AE(279): Loading Texture...
12-14 11:34:58.653: D/dalvikvm(279): GC_FOR_MALLOC freed 11 objects / 464 bytes in 44ms
12-14 11:34:58.663: I/dalvikvm-heap(279): Grow heap (frag case) to 7.040MB for
1048592-byte allocation
12-14 11:34:58.743: D/dalvikvm(279): GC_FOR_MALLOC freed 2 objects / 80 bytes in 75ms
12-14 11:34:58.973: I/System.out(279): started document!
...
12-14 11:43:05.393: I/jPCT-AE(279): Memory usage before compacting: 5867 KB used out
of 6215 KB
12-14 11:43:05.453: D/dalvikvm(279): GC_EXPLICIT freed 2560 objects / 145712 bytes in
61ms
12-14 11:43:05.503: D/dalvikvm(279): GC_EXPLICIT freed 295 objects / 21448 bytes in
51ms
12-14 11:43:05.717: I/jPCT-AE(279): Memory usage after compacting: 5705 KB used out of
6215 KB
...
12-14 11:43:05.792: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 105 objects / 6152 bytes
in 56ms
12-14 11:43:05.855: D/dalvikvm(279): GC_FOR_MALLOC freed 3 objects / 80 bytes in 51ms
...
12-14 11:43:12.863: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 864 objects / 1099072
bytes in 70ms
12-14 11:43:13.053: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 45 objects / 1760 bytes
in 55ms
12-14 11:43:14.533: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 49 objects / 2376 bytes
in 58ms
12-14 11:43:14.933: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 34 objects / 1408 bytes
in 55ms
12-14 11:43:15.423: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 13 objects / 504 bytes in
58ms
12-14 11:43:15.953: D/dalvikvm(279): GC_EXTERNAL_ALLOC freed 13 objects / 520 bytes in
56ms
...
12-14 11:43:31.203: I/jPCT-AE(279): Visibility lists disposed!
12-14 11:43:31.203: I/jPCT-AE(279): All texture data unloaded from gpu!
12-14 11:43:31.203: I/jPCT-AE(279): Renderer disposed!
12-14 11:43:31.203: I/jPCT-AE(279): Static references cleared...
...
12-14 11:43:36.943: E/dalvikvm-heap(279): 2964320-byte external allocation too large
for this process.
12-14 11:43:36.953: E/GraphicsJNI(279): VM won't let us allocate 2964320 bytes
12-14 11:43:36.953: D/AndroidRuntime(279): Shutting down VM
12-14 11:43:36.953: W/dalvikvm(279): threadid=1: thread exiting with uncaught
exception (group=0x4001d800)
12-14 11:43:36.973: E/AndroidRuntime(279): FATAL EXCEPTION: main
12-14 11:43:36.973: E/AndroidRuntime(279): android.view.InflateException: Binary XML
file line #33: Error inflating class <unknown>
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.view.LayoutInflater.createView(LayoutInflater.java:513)
12-14 11:43:36.973: E/AndroidRuntime(279): at
com.android.internal.policy.impl.PhoneLayoutInflater.
onCreateView(PhoneLayoutInflater.java:56)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:563)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.view.LayoutInflater.rInflate(LayoutInflater.java:618)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.view.LayoutInflater.rInflate(LayoutInflater.java:621)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.view.LayoutInflater.inflate(LayoutInflater.java:407)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.view.LayoutInflater.inflate(LayoutInflater.java:320)
12-14 11:43:36.973: E/AndroidRuntime(279): at
com.ai.ultimap.views.Manual.onItemClick(Manual.java:467)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.widget.AdapterView.performItemClick(AdapterView.java:284)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.widget.AbsListView$PerformClick.run(AbsListView.java:1696)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.os.Handler.handleCallback(Handler.java:587)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.os.Handler.dispatchMessage(Handler.java:92)
12-14 11:43:36.973: E/AndroidRuntime(279): at android.os.Looper.loop(Looper.java:123)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.app.ActivityThread.main(ActivityThread.java:4627)
12-14 11:43:36.973: E/AndroidRuntime(279): at
java.lang.reflect.Method.invokeNative(Native Method)
12-14 11:43:36.973: E/AndroidRuntime(279): at
java.lang.reflect.Method.invoke(Method.java:521)
12-14 11:43:36.973: E/AndroidRuntime(279): at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
12-14 11:43:36.973: E/AndroidRuntime(279): at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
12-14 11:43:36.973: E/AndroidRuntime(279): at dalvik.system.NativeStart.main(Native
Method)
12-14 11:43:36.973: E/AndroidRuntime(279): Caused by:
java.lang.reflect.InvocationTargetException
12-14 11:43:36.973: E/AndroidRuntime(279): at android.widget.ImageView.<init>
(ImageView.java:108)
12-14 11:43:36.973: E/AndroidRuntime(279): at
java.lang.reflect.Constructor.constructNative(Native Method)
12-14 11:43:36.973: E/AndroidRuntime(279): at
java.lang.reflect.Constructor.newInstance(Constructor.java:446)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.view.LayoutInflater.createView(LayoutInflater.java:500)
12-14 11:43:36.973: E/AndroidRuntime(279): ... 18 more
12-14 11:43:36.973: E/AndroidRuntime(279): Caused by: java.lang.OutOfMemoryError:
bitmap size exceeds VM budget
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.graphics.Bitmap.nativeCreate(Native Method)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.graphics.Bitmap.createBitmap(Bitmap.java:468)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.graphics.Bitmap.createBitmap(Bitmap.java:435)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.graphics.Bitmap.createScaledBitmap(Bitmap.java:340)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.graphics.BitmapFactory.finishDecode(BitmapFactory.java:488)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:462)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:323)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.graphics.drawable.Drawable.createFromResourceStream(Drawable.java:697)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.content.res.Resources.loadDrawable(Resources.java:1709)
12-14 11:43:36.973: E/AndroidRuntime(279): at
android.content.res.TypedArray.getDrawable(TypedArray.java:601)
12-14 11:43:36.973: E/AndroidRuntime(279): at android.widget.ImageView.<init>
(ImageView.java:118)
12-14 11:43:36.973: E/AndroidRuntime(279): ... 22 more
12-14 11:43:38.763: I/Process(279): Sending signal. PID: 279 SIG: 9
As you can see I'm specifically running into an outofmemory error during an ~3 MB bitmap load... This doesn't make sense to me since GC recently ran and nothing allocated since should have brought the VM within 3MB of capacity (256 MB). Is there only a small percentage of that 256 MB system RAM which is actually given to the VM before it crashes? Could it be that the Bitmap loading process has its own memory allocation cap? I know object pooling is a good way to try to avoid GC during game loops, but without knowing EXACTLY what triggers Dalvik GC we're still placing an awful lot of faith in the OS and Google's vague discussions of performance best-practices.
Can the GC state (e.g. 'about to run', 'running', 'finished running') be tracked from code so that large resource allocations might be planned strategically around available memory? I have read this post on the matter: Determine when the Android GC runs which offers an interesting potential solution, but still relies on a 'trick'. I'd like to know if there is a supported API call somewhere which can be relied upon in production code (not just debug) to track the precise state of the garbage collector. System.gc() might be useful in some cases IF GC state can be checked; otherwise, since it can't promise an immediate GC run, its usefulness drops quite a bit.
GC是否总是在系统范围内,或者可以单独的线程(例如游戏的专用渲染线程)逃避GC引起的潜在性能滞后问题？
Given the following hypothetical scenario: 'I have an object which costs (VM RAM budget)/2 bytes to instantiate, and I instantiate it immediately with a single reference. I then null out that reference, making the object eligible for GC but of course not actually releasing its memory yet. I then immediately instantiate the object again.' Would this crash the VM or is there some way the OS handles such extreme situations automatically to avoid crashing the VM? If the OS doesn't handle it, I would cite this as a good example of why my question #2 above is valid; if GC state could be tracked, logic could be included in the source to handle huge object allocation issues (in reality more likely to be large resources than badly designed classes) by checking to see if memory from a GC eligible object had been freed before loading the new huge object instance, and showing a small loading animation while polling GC in the background. This should avoid application not responding errors as well as legitimate out of memory errors... Some sort of onGC() listener would be ideal; could a GC listener be implemented in native code without re-building the OS kernel?
5.最后,一些源代码......对于性能高效的Android编程,我有正确的想法吗？
活动类:
package com.ai.ultimap;
//imports omitted...
public class UltiMapActivity extends Activity {
//Housekeeping
private String viewDriverID = "";
private static final int TUTORIAL = 7;
//visuals
private HomeView hv; //home view
private ConfigView cv; //config view
private MapView mv; //map view
private Manual man; //manual view
private int manCount = 0; //tracks the number of times the manual has been called
//with menu button, ignoring button presses unless value is zero
private PathCreator pcv; //path creator view
private MasterGL mgl; //the gl center
private String pending = "Coming soon...";
private PathCreator draw;
private Surfacer morlock;
// Used to handle pause and resume...
private static UltiMapActivity master;
//XML I/O considerations
private String fXML = "mypaths.xml";
private String sXML = "data was not saved properly...?";
private FileOutputStream fos;
private FileInputStream fis;
private FileWriter fw;
private FileReader fr;
private Date theDate = new Date();
private char[] buf = new char[1];
//Feedback stuffs
private FeedbackController feed;
//tracking you... :)
private WifiStalk stalk;
private long lat;
private long longitude;
//Testing
private DrawView dv;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d("me","ultimap created!");
master = null;
mgl = new MasterGL(this); //revisit this later for versatility
man = new Manual(this);
feed = new FeedbackController(this);
stalk = new WifiStalk(this);
draw = new PathCreator(this);
hv = new HomeView(this,draw);
try {
BeanCounter bean = new BeanCounter(this);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (XmlPullParserException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
showDialog(TUTORIAL);
}
@Override
public boolean onKeyDown(int keyCode,KeyEvent e){
if (keyCode == 82){
if (viewDriverID.equals("hv")){
hv.removeHV();
}
else if (viewDriverID.equals("cv")){
cv.removeCV();
}
else if (viewDriverID.equals("mv")){
return true;
}
else if (viewDriverID.equals("pcv")){
return true;
}
if(man.getAddedState() == 0){
//Show the manual code...
System.out.println("View we're coming from: " + this.getVDID());
Log.e("me", "man.getaddedstate does equal 0, should be about to makeMan");
man.makeMan();
}
else if(man.getAddedState() == 2){
man.removeMan();
man.removeMan2();
man.setAddedState(1);
}
else if(man.getAddedState() == 1){
System.out.println("View we're coming from: " + this.getVDID());
man.addMan();
}
}
return true;
}
@Override
protected Dialog onCreateDialog(int id) {
//alerts ommitted for space
}
//Used to track the semantic context of what the Activity is displaying
//Getters/setters for external access ommitted
@Override
protected void onStart(){
super.onStart();
Log.d("me","ultimap started!");
}
@Override
protected void onPause() {
super.onPause();
Log.d("me","ultimap paused!");
if (mgl.getGLview() != null){
mgl.getGLview().onPause();
}
if (draw.getGLV() != null){
draw.getGLV().onPause();
}
}
@Override
protected void onResume() {
super.onResume();
Log.d("me","ultimap resumed!");
stalk.killListener();
if (mgl.getGLview() != null){
mgl.getGLview().onResume();
Log.d("me", "mgl.getGLview is NOT null on resume");
}
else if (mgl.getGLview() == null){
mgl.initGL();
mgl.getGLview().onResume();
Log.d("me", "mgl.getGLview is null on resume");
}
if (draw.getGLV() != null){
draw.getGLV().onResume();
Log.d("me", "draw.getGLV is NOT null on resume");
}
else if (draw.getGLV() == null && draw.getHGL() != null){
draw.pcvInit();
Log.d("me", "draw.getGLV is null on resume");
}
if (hv.getMV() != null && hv.getMV().getGLV() != null){
hv.getMV().getGLV().onResume();
Log.d("me", "map.getGLV is NOT null on resume");
}
else if (hv.getMV() != null && hv.getMV().getGLV() == null &&
hv.getMV().getHGL() != null){
hv.getMV().mvInit();
Log.d("me", "map.getGLV is null on resume");
}
}
@Override
protected void onStop() {
super.onStop();
//feed.getSP().release();
Log.d("me","ultimap stopped!");
}
@Override
protected void onRestart(){
super.onRestart();
Log.d("me","ultimap restarted!");
if (mgl != null){
mgl.initGL();
}
}
@Override
protected void onDestroy(){
super.onDestroy();
Log.d("me","ultimap destroyed!");
mgl.disposeTextures();
if (feed.getSP() != null && feed.getSID() != 0 && feed.getLoaded() ==
true){
feed.getSP().unload(feed.getSID());
feed.getSP().release();
}
}
}
教程视图管理器类:
/*
* This class defines an in-app manual which is callable/dismissable
* in a non-invasive way...
*
* http://www.codeproject.com/KB/android/ViewFlipper_Animation.aspx
*http://developer.android.com/reference/android/widget/
*ViewFlipper.html#ViewFlipper%28android.content.Context%29
* http://developer.android.com/resources/articles/avoiding-memory-leaks.html
*/
package com.ai.ultimap.views;
//imports ommitted
public class Manual extends View implements OnItemClickListener{
private UltiMapActivity hUMA;
private ListView lv1;
private ListAdapter la;
private LayoutInflater mInflater;
private Vector<RowData> data;
private TextView tv;
private RelativeLayout holderRL;
private View v;
private View v2;
private int addedState = 0; //tracks whether or not a view has been instantiated,
//and if so whether or not it is the currently visible view
private int addedState2 = 0;
//Grid View stuff
private GridView helpGrid;
//ViewFlipper stuff
private ViewFlipper vf;
private TextView tutTV;
private String mapTutString = "Map View Tutorial Part: ";
private String pcTutString = "Path Creator Tutorial Part: ";
private String tutType;
private TextView counterTV;
private int partCounter = 1;
private float oldTouchValue = 0.0f;
private boolean searchOk = true;
private ImageView floatingImage;
public Manual(UltiMapActivity hAct){
super(hAct);
hUMA = hAct;
holderRL = new RelativeLayout(hUMA);
v = new View(hUMA);
floatingImage = new ImageView(hUMA);
}
//Here we summon and populate the grid view
public void makeMan(){
if (addedState == 0){
Log.e("me", "in makeMan");
mInflater = (LayoutInflater)
hUMA.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
hUMA.addContentView(holderRL, new
LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.MATCH_PARENT));
v = mInflater.inflate(R.layout.helpgrid, holderRL, false);
helpGrid = (GridView) v.findViewById(R.id.manGV);
helpGrid.setAdapter(new ImageAdapter(hUMA));
hUMA.addContentView(v, new
LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.MATCH_PARENT));
helpGrid.setOnItemClickListener(this);
addedState = 2;
}
}
public void addMan(){
if (v != null && addedState == 1){
v.setVisibility(VISIBLE);
v.bringToFront();
addedState = 2;
}
}
public void addMan2(){
if (v2 != null && addedState2 == 1){
v2.setVisibility(VISIBLE);
v2.bringToFront();
addedState2 = 2;
}
}
public void removeMan(){
if (v != null && addedState == 2){
v.setVisibility(GONE);
addedState = 1;
String s = hUMA.getVDID();
if (s.equals("hv")){
hUMA.getHome().addHV();
Log.d("me", "add hjomeview called from anual");
Log.d("me", "hv addedstate : " +
hUMA.getHome().getAddedState());
}
else if (s.equals("cv")){
hUMA.getConfig().addCV();
}
else if (s.equals("mv")){
hUMA.getHome().getMV().mvInit();
}
else if (s.equals("pcv")){
hUMA.getDraw().pcvInit();
}
}
}
public void removeMan2(){
if (v2 != null && addedState2 == 2){
v2.setVisibility(GONE);
addedState2 = 1;
String s = hUMA.getVDID();
if (s.equals("hv")){
hUMA.getHome().addHV();
Log.d("me", "add hjomeview called from manual");
Log.d("me", "hv addedstate : " +
hUMA.getHome().getAddedState());
}
else if (s.equals("cv")){
hUMA.getConfig().addCV();
}
else if (s.equals("mv")){
hUMA.getHome().getMV().mvInit();
}
else if (s.equals("pcv")){
hUMA.getDraw().pcvInit();
}
}
}
//addedstate getters and setters ommitted for space
@Override
public boolean onTouchEvent(MotionEvent touchevent) {
switch (touchevent.getAction())
{
case MotionEvent.ACTION_DOWN:
{
System.out.println("received a touch down at " + touchevent.getX()
+ "," + touchevent.getY());
oldTouchValue = touchevent.getX();
if(this.searchOk==false) return false;
float currentX = touchevent.getX();
if (currentX > (vf.getWidth()/2))
{
vf.setInAnimation(AnimationHelper.inFromRightAnimation());
vf.setOutAnimation(AnimationHelper.outToLeftAnimation());
vf.showNext();
if (partCounter <= 3 && partCounter >= 1){
partCounter++;
}
else if (partCounter == 4){
partCounter = 1;
}
else{
Log.e("me", "partCounter got past 4...");
}
if(tutType.equals("map")){
counterTV.setText(mapTutString + partCounter);
}
else if(tutType.equals("pc")){
counterTV.setText(pcTutString + partCounter);
}
else{
Log.e("me","not getting valid tutType string");
}
}
if (currentX <= (vf.getWidth()/2))
{
vf.setInAnimation(AnimationHelper.inFromLeftAnimation());
vf.setOutAnimation(AnimationHelper.outToRightAnimation());
vf.showPrevious();
if (partCounter >= 2 && partCounter <= 4){
partCounter--;
}
else if (partCounter == 1){
partCounter = 4;
}
else{
Log.e("me", "partCounter got below 1...");
}
if(tutType.equals("map")){
counterTV.setText(mapTutString + partCounter);
}
else if(tutType.equals("pc")){
counterTV.setText(pcTutString + partCounter);
}
else{
Log.e("me","not getting valid tutType string");
}
}
break;
}
case MotionEvent.ACTION_UP:
{
//nothing to do here
}
}
return false;
}
public void setUserText(String str){
tv.setText(str);
}
private class CustomTV extends TextView{
private String content = "";
public CustomTV(Context c, String str){
super(c);
content = str;
this.setText(content);
}
}
/**
* Data type used for custom adapter. Single item of the adapter.
*/
private class RowData {
protected String mItem;
protected String mDescription;
RowData(String item, String description){
mItem = item;
mDescription = description;
}
@Override
public String toString() {
return mItem + " " + mDescription;
}
}
private class CustomAdapter extends ArrayAdapter<RowData> {
public CustomAdapter(Context context, int resource,
int textViewResourceId, List<RowData> objects) {
super(context, resource, textViewResourceId, objects);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
//widgets displayed by each item in your list
TextView item = null;
TextView description = null;
//data from your adapter
RowData rowData= getItem(position);
//we want to reuse already constructed row views...
if(null == convertView){
convertView = mInflater.inflate(R.layout.custom_row, null);
holder = new ViewHolder(convertView);
convertView.setTag(holder);
}
holder = (ViewHolder) convertView.getTag();
item = holder.getItem();
item.setText(rowData.mItem);
description = holder.getDescription();
description.setText(rowData.mDescription);
return convertView;
}
}
/**
* Wrapper for row data.
*
*/
private class ViewHolder {
private View mRow;
private TextView description = null;
private TextView item = null;
public ViewHolder(View row) {
mRow = row;
}
public TextView getDescription() {
if(null == description){
description = (TextView) mRow.findViewById(R.id.cbox);
}
return description;
}
public TextView getItem() {
if(null == item){
item = (TextView) mRow.findViewById(R.id.cbox2);
}
return item;
}
}
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int position, long id) {
v.setVisibility(GONE);
if (addedState2 == 0){
hUMA.addContentView(this,DefineLayoutParams.getParams(DefineLayoutParams.getMM()));
//this is why the onTouch only starts lsitening at this point
if (position == 0){
v2 = mInflater.inflate(R.layout.flipper, holderRL, false);
vf = (ViewFlipper) v2.findViewById(R.id.manFlipperVF);
tutTV = (TextView) v2.findViewById(R.id.manDescriptionTV);
counterTV = (TextView) v2.findViewById(R.id.mapviewtutCounterTV);
tutTV.setText("Map View Instructions: ...");
counterTV.setText(mapTutString + partCounter);
tutType = "map";
}
else if (position == 1){
v2 = mInflater.inflate(R.layout.flipperpc, holderRL, false);
vf = (ViewFlipper) v2.findViewById(R.id.manFlipperpcVF);
tutTV = (TextView) v2.findViewById(R.id.manDescriptionpcTV);
counterTV = (TextView) v2.findViewById(R.id.manFlipperCounterpcTV);
tutTV.setText("Path Creator Tutorial:...");
counterTV.setText(pcTutString + partCounter);
tutType = "pc";
}
addedState2 = 2;
hUMA.addContentView(v2, DefineLayoutParams.getParams(DefineLayoutParams.getWW()));
}
else if(addedState2 == 1){
v2.setVisibility(VISIBLE);
addedState2 = 2;
}
}
public String getTutType(){
return tutType;
}
}
教程查看Flipper XML:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<ScrollView
android:id="@+id/manDerscriptionSV"
android:layout_width="match_parent"
android:layout_height="200px"
>
<TextView
android:id="@+id/manDescriptionTV"
android:text="Coming Soon..."
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>
</ScrollView>
<TextView
android:id="@+id/mapviewtutCounterTV"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Map View Tutorial Part: "
android:gravity="center"
android:layout_below="@id/manDerscriptionSV"
/>
<ViewFlipper
android:id="@+id/manFlipperVF"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/mapviewtutCounterTV"
>
<ImageView
android:id="@+id/mapviewtut1"
android:src="@drawable/mapviewtutflipper1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>
<ImageView
android:id="@+id/mapviewtut2"
android:src="@drawable/mapviewtutflipper2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>
<ImageView
android:id="@+id/mapviewtut3"
android:src="@drawable/mapviewtutflipper3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>
<ImageView
android:id="@+id/mapviewtut4"
android:src="@drawable/mapviewtutflipper4"
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>
</ViewFlipper>
</RelativeLayout>
谢谢,CCJ
Com*_*are 23
- 究竟是什么触发了Android中的GC？
这是SDK开发人员不应该担心的内部实现细节.
我见过的其他VM实现通常允许在GC收到运行信号之前将一定比例的系统内存分配给应用程序.
我会接受你的话.Java不会这样做.JVM并不关心存在多少系统内存 - 它最多只关心-Xmx它自己的VM的潜在堆大小(例如).
然而,扫描以下LogCat似乎表明Dalvik GC至少部分地运行
正确.特别是在较新版本的Android上,GC在其自己的线程中并发运行,而不是之前采用的stop-the-world方法.
这对我来说没有意义,因为GC最近运行并且没有任何分配,因为应该将VM带入3MB容量(256 MB).
您的VM拥有256MB的堆空间是不太可能的.根据您的设备,它可能低至16MB.
此外,Android没有压缩GC算法,因此即使您可能有超过3MB的空间,也可能没有连续的3MB块.
这就是为什么它是通往重要recycle()的Bitmap对象或尝试重用他们(如inBitmap中BitmapOptions,在API等级11加).
此外,您可以使用DDMS创建堆转储和MAT来检查它,以更准确地确定您的内存在哪里以及谁在抓住什么.这在Android 3.0+上效果更好,因为MAT将能够Bitmap在这些版本中更准确地报告内存.
是否只有一小部分256 MB的系统RAM在VM崩溃之前实际给予它？
是.它被称为堆.Android设备具有堆大小限制.通常,它在16-48MB范围内,具体取决于Android OS版本和屏幕分辨率.
可能是Bitmap加载过程有自己的内存分配上限吗？
不,它在相同的堆大小预算下工作.从Android 3.0开始,它确实将内存加载到与其他Dalvik对象相同的堆中 - 以前,它使用堆外部的系统RAM块,但空间是根据堆的大小预算计算的.
但是,如果不确切地知道是什么触发了Dalvik GC,我们仍然对操作系统和Google对性能最佳实践的模糊讨论抱有极大的信心
正如他们所说,生活还在继续.
是否可以从代码中跟踪GC状态(例如"即将运行","运行","完成运行"),以便可以围绕可用内存战略性地规划大量资源分配？...我想知道某个地方是否存在支持的API调用,可以依赖于生产代码(而不仅仅是调试)来跟踪垃圾收集器的精确状态.
没有.
GC是否总是在系统范围内,或者可以单独的线程(例如游戏的专用渲染线程)逃避GC引起的潜在性能滞后问题？
对于任何VM,GC都不是"系统范围的".GC始终位于VM中.
在较新版本的Android上,GC是并发的,因此在正常情况下不会实质性地阻止任何线程.在旧版Android上,GC是世界各地的,会影响所有线程.对于Android 3.0而言,这种变化肯定已经到位 - 我的内存对于并发GC是否已经适用于Android 2.3而言仍然很模糊.您可能希望观看有关Android内存管理的2011年Google I | O演示文稿.
这会使VM崩溃还是某种方式操作系统会自动处理这种极端情况以避免崩溃VM？
Android应该在提升之前强制立即使用GC OutOfMemoryException.根据我之前的paragaraph,这种情况不符合"正常情况".
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