Android基于Window.ID

Android基于Window.ID_ANDROID_CONTENT给定id添加子View

这一技术特点在一些视频播放器中比较有用。

例如代码：

package zhangphil.demo; import android.app.Activity; import android.content.Context; import android.content.ContextWrapper; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.Gravity; import android.view.View; import android.view.ViewGroup; import android.view.Window; import android.widget.FrameLayout; public class MainActivity extends AppCompatActivity { private static final int VIEW_ID = 0xf0a01; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //setContentView(R.layout.activity_main); int w = 500; int h = 500; int gap = 100; addView(w, h, getResources().getColor(android.R.color.holo_orange_light)); addView(w - gap, h - gap, getResources().getColor(android.R.color.holo_green_light)); addView(w - gap * 2, h - gap * 2, getResources().getColor(android.R.color.holo_red_light)); } private void addView(int w, int h, int color) { ViewGroup vp = (ViewGroup) (scanForActivity(this))//.getWindow().getDecorView(); .findViewById(Window.ID_ANDROID_CONTENT); View old = vp.findViewById(VIEW_ID); if (old != null) { vp.removeView(old); } FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(w, h, Gravity.CENTER); FrameLayout newView = new FrameLayout(this); newView.setBackgroundColor(color); newView.setId(VIEW_ID); vp.addView(newView, params); } public static Activity scanForActivity(Context context) { if (context == null) return null; if (context instanceof Activity) { return (Activity) context; } else if (context instanceof ContextWrapper) { return scanForActivity(((ContextWrapper) context).getBaseContext()); } return null; } }

运行结果：

如果在addView里面把这段代码注释掉：

// View old = vp.findViewById(VIEW_ID); // if (old != null) { // vp.removeView(old); // }

运行结果。

这一特性如果巧妙加以利用可制作成特殊视频view的呈现。