在Android中同步两个水平滚动视图

Question

我尝试按照这篇文章中的建议同步ScrollView滚动位置 - 安卓 但遇到了问题.

背景 - 我想要一个包含水平和垂直滚动的表格布局,但我希望第一行和第一列始终存在 - 就像使用excel的冻结窗格一样.不幸的是,Android java编程似乎几乎不可能......让我头疼不已.我已经设置好了,如果我可以同步这两个horizo​​ntalscrollviews,那么我将按照我想要的方式工作.

我按照上面发布的链接的建议,我遇到的问题是这个.当我实施时,应用程序强制关闭

scrollView1.setScrollViewListener(本);

我认为问题可能是我声明ObservableScrollViews的方式.我没有使用XML - 所有对象都是以编程方式创建的.我试过用

private ObservableScrollView oScrollViewOne = new ObservableScrollView(this);

但这也导致了一股力量关闭.(我可以创建一个常规的滚动视图,为其分配一个ID,然后使用

scrollView1 =(ObservableScrollView)findViewById(ID); 其中ID是我给滚动视图的整数.

我想知道如何使用下面的注释以及如果我不使用XML布局如何使用它们.

我们应该在布局中指定这个新的ObservableScrollView类,而不是现有的ScrollView标记.

com.test.ObservableScrollView android:id ="@ + id/scrollview1"......

使用显式代码实现同步两个horizo​​ntalscroll视图的任何其他建议 - 不仅仅是建议使用OnTouchMotionEvent或其他想法而不提供代码,正如我之前看到的那样.

这是错误代码

10-23 23:33:08.631: ERROR/AndroidRuntime(18187): FATAL EXCEPTION: main
10-23 23:33:08.631: ERROR/AndroidRuntime(18187): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.glen.apps.TeacherAidePro/com.glen.apps.TeacherAidePro.TeacherAidePro}: java.lang.NullPointerException
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2709)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2803)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.app.ActivityThread.access$2300(ActivityThread.java:135)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2136)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.os.Looper.loop(Looper.java:144)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.app.ActivityThread.main(ActivityThread.java:4937)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at java.lang.reflect.Method.invokeNative(Native Method)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at java.lang.reflect.Method.invoke(Method.java:521)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at dalvik.system.NativeStart.main(Native Method)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187): Caused by: java.lang.NullPointerException
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.content.ContextWrapper.getResources(ContextWrapper.java:80)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.view.View.<init>(View.java:1810)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.view.View.<init>(View.java:1856)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.view.ViewGroup.<init>(ViewGroup.java:299)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.widget.FrameLayout.<init>(FrameLayout.java:83)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.widget.ScrollView.<init>(ScrollView.java:137)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.widget.ScrollView.<init>(ScrollView.java:133)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.widget.ScrollView.<init>(ScrollView.java:129)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at com.glen.apps.TeacherAidePro.ObservableScrollView.<init>(ObservableScrollView.java:12)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at com.glen.apps.TeacherAidePro.TeacherAidePro.<init>(TeacherAidePro.java:119)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at java.lang.Class.newInstanceImpl(Native Method)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at java.lang.Class.newInstance(Class.java:1429)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.app.Instrumentation.newActivity(Instrumentation.java:1036)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2701)
10-23 23:33:08.631: ERROR/AndroidRuntime(18187):     ... 11 more

这是第12行

 1. package com.glen.apps.TeacherAidePro;
 2.
 3. import android.content.Context;
 4. import android.util.AttributeSet;
 5. import android.widget.ScrollView;
 6.
 7. public class ObservableScrollView extends ScrollView {
 8.
 9.   private IScrollListener listener = null;    
10.
11.   public ObservableScrollView(Context context) {
12.       super(context);
  }

Answer 1

该错误指向ObservableScrollView中构造函数中的空指针.你可以自己发布构造函数以及第12行吗？

我看到的XML和自定义滚动视图交互方式的一个可能问题是您的自定义滚动视图是一个内部类.有关如何在XML中声明内部类自定义组件或将其移动到外部类的信息,请参阅此页面.我通常把它放在一个外部类中,但是如果你想把它作为一个内部类,那就像是

<view
    class="com.glen.apps.TeacherAidePro$ObservableScrollView"
.../>

我不认为这解释了你的空指针异常,所以请发布你的ObservableScrollView类.

编辑:

如果你坚持用Java做所有事情,这是一个有效的例子:

private ObservableScrollView scrollView1 = null;
private ObservableScrollView scrollView2 = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    LinearLayout parent = new LinearLayout(this);
    parent.setOrientation(LinearLayout.HORIZONTAL);
    parent.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,
            LayoutParams.FILL_PARENT));
    parent.setWeightSum(2.0f);

    scrollView1 = new ObservableScrollView(this);
    scrollView1.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,
            LayoutParams.FILL_PARENT, 1.0f));
    scrollView2 = new ObservableScrollView(this);
    scrollView2.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,
            LayoutParams.FILL_PARENT, 1.0f));

    scrollView1.setScrollViewListener(new ScrollViewListener() {
        public void onScrollChanged(ObservableScrollView scrollView, int x,
                int y, int oldx, int oldy) {
            scrollView2.scrollTo(x, y);
        }
    });
    scrollView2.setScrollViewListener(new ScrollViewListener() {
        public void onScrollChanged(ObservableScrollView scrollView, int x,
                int y, int oldx, int oldy) {
            scrollView1.scrollTo(x, y);
        }
    });

    TextView tv1 = new TextView(this);
    tv1.setText("TEXT1TEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXT");
    tv1.setTextSize(36.0f);
    scrollView1.addView(tv1);

    TextView tv2 = new TextView(this);
    tv2.setText("TEXT2TEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXTTEXT");
    tv2.setTextSize(36.0f);
    scrollView2.addView(tv2);

    parent.addView(scrollView1);
    parent.addView(scrollView2);
    parent.invalidate();

    setContentView(parent);
}

基本上,这会创建两个并排的滚动视图,每个重量为1.0,并将它们放在一个LinearLayout中,总重量在2.0的布局上,因此它们各自得到宽度的一半.

但是,我强烈建议习惯使用XML,因为创建布局要容易得多(在我看来).发现错误也更容易,嵌套的XML形式使其更易于阅读.无论如何,希望这可以解决问题.