Activity的onCreate方法中通常利用布局文件来构建ContentView。另一种比较实用的方法是：在代码中动态创建ContentView。如下所示：

@Overridepublic void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    gestureScanner = new GestureDetector(this);    gestureScanner.setOnDoubleTapListener(doubleTapListener);    main = new LinearLayout(this);    main.setBackgroundColor(Color.GRAY);    main.setLayoutParams(new LinearLayout.LayoutParams(320, 480));    main.setOrientation(LinearLayout.VERTICAL);    viewA = new TextView(this);    viewA.setBackgroundColor(Color.YELLOW);    viewA.setTextColor(Color.BLACK);    viewA.setTextSize(16);    viewA.setLayoutParams(new LinearLayout.LayoutParams(320, 50));    main.addView(viewA);    setContentView(main);}