难以创建我自己的自定义视图

Question

所以我试图创建自己的视图之外的XML布局，并难以让它显示任何东西。我确信我错过了一些简单的东西，但看不到它会是什么。任何输入赞赏。这里是我用于测试目的的两个类。

public class TestSuite extends Activity { 

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

     // Turns off the application title at the top.. 
     requestWindowFeature(Window.FEATURE_NO_TITLE); 
     // Turns off the status bar at the top.. 
     getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); 

     setContentView(new Background(this)); 
    } 
} 

和

public class Background extends View { 

    public Background(Context context) { 
     super(context); 
    } 

    public Background(Context context, AttributeSet attrs) { 
     super(context, attrs); 
    } 

    public Background(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attrs, defStyle); 
    } 

    @Override 
    public void onDraw(Canvas canvas) { 
     super.onDraw(canvas); 

     Resources res = getResources(); 

     Rect baseRectBounds = new Rect(0,0,200,200); 
     Rect topRectBounds = new Rect(20,20,160,160); 
     Rect bottomRectBounds = new Rect(40,40,120,120); 

     Paint baseColor = new Paint(res.getColor(R.color.blue)); 
     Paint topColor = new Paint(res.getColor(R.color.red)); 
     Paint bottomColor = new Paint(res.getColor(R.color.green)); 

     canvas.drawRect(baseRectBounds, baseColor); 
     canvas.drawRect(topRectBounds, topColor); 
     canvas.drawRect(bottomRectBounds, bottomColor); 
    } 

} 

编辑

下面是最新的onDraw方法我的工作。是

@Override 
public void onDraw(Canvas canvas) { 
    super.onDraw(canvas); 

    Resources res = getResources(); 

    Rect canvasBounds = canvas.getClipBounds(); 

    Log.v("CanvasBounds before", "left - " + canvasBounds.left); 
    Log.v("CanvasBounds before", "top - " + canvasBounds.top); 
    Log.v("CanvasBounds before", "right - " + canvasBounds.right); 
    Log.v("CanvasBounds before", "bottom - " + canvasBounds.bottom); 

    Rect baseRect = new Rect(0,0,200,200); 
    Rect topRect = new Rect(20,20,160,160); 
    Rect botRect = new Rect(40,40,120,120); 

    Paint baseColor = new Paint(res.getColor(R.color.red)); 
    Paint topColor = new Paint(res.getColor(R.color.green)); 
    Paint botColor = new Paint(res.getColor(R.color.blue)); 
    baseColor.setStyle(Style.FILL); 
    topColor.setStyle(Style.FILL); 
    botColor.setStyle(Style.FILL); 

    canvas.drawRect(baseRect, baseColor); 
    canvas.drawRect(topRect, topColor); 
    canvas.drawRect(botRect, botColor); 

    canvasBounds = canvas.getClipBounds(); 

    Log.v("CanvasBounds after", "left - " + canvasBounds.left); 
    Log.v("CanvasBounds after", "top - " + canvasBounds.top); 
    Log.v("CanvasBounds after", "right - " + canvasBounds.right); 
    Log.v("CanvasBounds after", "bottom - " + canvasBounds.bottom); 
} 

日志语句的结果如下：

CanvasBounds before left - 0 
CanvasBounds before top - 0 
CanvasBounds before right - 480 
CanvasBounds before bottom - 800 
CanvasBounds after left - 0 
CanvasBounds after top - 0 
CanvasBounds after right - 480 
CanvasBounds after bottom - 800 

完成编辑

由于泰德的帮助，这是我最后的onDraw方法（别人谁可能需要它） 。

@Override 
public void onDraw(Canvas canvas) { 
    super.onDraw(canvas); 

    Resources res = getResources(); 

    Rect baseRect = new Rect(0,0,200,200); 
    Rect topRect = new Rect(20,20,160,160); 
    Rect botRect = new Rect(40,40,120,120); 

    Paint color = new Paint(); 

    color.setColor(res.getColor(R.color.red)); 
    canvas.drawRect(baseRect, color); 
    color.setColor(res.getColor(R.color.blue)); 
    canvas.drawRect(topRect, color); 
    color.setColor(res.getColor(R.color.green)); 
    canvas.drawRect(botRect, color); 
} 

Answer 1

两个建议：

在c'tor
1. ，调用setLayoutParams(new LayoutParams(FILL_PARENT, FILL_PARENT))（这里，LayoutParams是ViewGroup.LayoutParams）
2. 覆盖measure(int,int)并实现其作为docs for View