Android基于Window.ID_ANDROID_CONTENT给定id添加子View

比眉伴天荒 2024-02-18 14:06 6阅读 0赞

**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：

![Center][]

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。

![Center 1][]

这一特性如果巧妙加以利用可制作成特殊视频view的呈现。

[Center]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/753eb8061d064648b665f310a23a6615.png
[Center 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/9c3168cdf33d45048df14db9331bf778.png