在Android Wear上实现GridViewPager的正确方法是什么？

Question

我正在尝试实现GridViewPager,因此我可以在2个独特的视图之间切换.到目前为止,我根本无法添加任何视图.以下是我的代码

public class Gridder extends Activity {

private TextView mTextView;
GridViewPager gridViewPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_gridder);
    final WatchViewStub stub = (WatchViewStub) findViewById(R.id.watch_view_stub);
    final LayoutInflater inflater = getLayoutInflater();
    stub.setOnLayoutInflatedListener(new WatchViewStub.OnLayoutInflatedListener() {
        @Override
        public void onLayoutInflated(WatchViewStub stub) {
            gridViewPager = (GridViewPager) findViewById(R.id.pager);
            gridViewPager.setAdapter(new MyGridViewPagerAdapter());
            gridViewPager.addView(inflater.inflate(R.layout.selector_generic, stub));;
        }
    });
}

private class MyGridViewPagerAdapter extends GridPagerAdapter {
    @Override
    protected void destroyItem(ViewGroup arg0, int arg1, int arg2, Object arg3) {
    }

    @Override
    public int getColumnCount(int arg0) {
        return 1;
    }

    @Override
    public int getRowCount() {
        return 1;
    }

    @Override
    protected Object instantiateItem(ViewGroup arg0, int arg1, int arg2) {
        return null;
    }

    @Override
    public boolean isViewFromObject(View arg0, Object arg1) {
        return false;
    }
}

在主视图存根的矩形子节点中,我有一个带有id寻呼机的GridViewPager,就像我在上面引用的那样:

<android.support.wearable.view.GridViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:keepScreenOn="true" />

此代码抛出非法状态异常并报告我的子视图已有父级.见下文

07-16 14:44:40.847  12940-12940/com.larvalabs.weartest E/AndroidRuntime? FATAL EXCEPTION: main
Process: com.larvalabs.weartest, PID: 12940
java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
        at android.view.ViewGroup.addViewInner(ViewGroup.java:3561)
        at android.view.ViewGroup.addView(ViewGroup.java:3414)
        at android.support.wearable.view.GridViewPager.addView(GridViewPager.java:1088)
        at android.view.ViewGroup.addView(ViewGroup.java:3359)
        at android.view.ViewGroup.addView(ViewGroup.java:3335)
        at com.larvalabs.weartest.Gridder$1.onLayoutInflated(Gridder.java:30)
        at android.support.wearable.view.WatchViewStub.inflate(WatchViewStub.java:133)
        at android.support.wearable.view.WatchViewStub.onMeasure(WatchViewStub.java:141)
        at android.view.View.measure(View.java:16648)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:16648)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2321)
        at android.view.View.measure(View.java:16648)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1959)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1145)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1340)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1032)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5657)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
        at android.view.Choreographer.doCallbacks(Choreographer.java:574)
        at android.view.Choreographer.doFrame(Choreographer.java:544)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5026)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

Stacktrace解释:

首先 - 以下行是错误的:

gridViewPager.addView(inflater.inflate(R.layout.selector_generic, stub));

inflate(int resource, ViewGroup root)
与root!=null相同
inflate(int resource, ViewGroup root, boolean attachToRoot) 与最后一个参数为true.

因此,根据文档,它将从视图中resource扩展视图并将其附加到root - >然后返回根.

这将尝试将新的膨胀视图附加到stub,然后尝试将stub(从inflate()指定的结果root)附加到gridViewPager.但是stub已经有一个父(它已经附加到你的活动中的视图层次结构).所以这是对堆栈跟踪的解释:)
请注意,您不应该向gridViewPagervia .addView()方法添加视图- 您应该通过适配器来执行此操作,并且应该删除该行.

GridPagerAdapter示例:

这是简单的实现GridPagerAdapter;

private class MyGridViewPagerAdapter extends GridPagerAdapter {
    @Override
    public int getColumnCount(int arg0) {
        return 2;
    }

    @Override
    public int getRowCount() {
        return 2;
    }

    @Override
    protected Object instantiateItem(ViewGroup container, int row, int col) {
        final View view = LayoutInflater.from(getApplicationContext()).inflate(R.layout.grid_view_pager_item, container, false);
        final TextView textView = (TextView) view.findViewById(R.id.textView);
        textView.setText(String.format("Page:\n%1$s, %2$s", row, col));
        container.addView(view);
        return view;
    }

    @Override
    protected void destroyItem(ViewGroup container, int row, int col, Object view) {
        container.removeView((View)view);
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view==object;
    }
}

内容grid_view_pager_item.xml:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="10dp">

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:layout_gravity="center_vertical"
        android:gravity="center"
        android:background="#4400ff00"
        android:textColor="#000000"
        android:textSize="26sp"/> 

</FrameLayout>

这是2x2网格的最终结果.两个屏幕处于静止状态,两个屏幕在半滚动的页面中被描绘:)

寻找更多？

这只是使用标准的一个例子GridPagerAdapter.如果你想更先进的之一,拥有的使用FragmentGridPagerAdapter,CardFragments和网页背景-请参阅GridViewPager位于平台的样品中例如:
{sdk_root}/samples/android-20/wearable/GridViewPager