Question

我想点击一个按钮并添加一个电阻。所以我需要的是在单击按钮时使视图无效。但是方法MyView内的update()内的无效值无效。我一直试图寻找这个问题，但我发现没有什么类似于我想做的事情，或者这可能不是这样做的。

DefaultActivity.java

public class DefaulActivity extends Activity {       

  MyView myView;

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

    setContentView(R.layout.main);
    myView = new MyView(this, null); 

    final Button bAddResistor = (Button) findViewById(R.id.bAdd);
    bAddResistor.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            // Perform action on click              
            myView.update();                            
            Log.d("ButtonADD", "Button Add has been clicked");
        }
    });          
  } 
}

MyView.java

public class MyView extends SurfaceView implements SurfaceHolder.Callback{      


  Resistor myResistor;
  private ArrayList<Resistor> mElements = new ArrayList<Resistor>();


  public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);  
    getHolder().addCallback(this);  

  } 

  @Override
  protected void onDraw(Canvas canvas) {

    super.onDraw(canvas);

    synchronized (mElements) {
        for (Resistor element : mElements) {
            element.doDraw(canvas);                
        }
    }   

  }

  public void update() {

       mElements.add(new Resistor(getContext(), (int) 10, (int) 10));
       invalidate(); //Does not work!
  }


  @Override
  public void surfaceChanged(SurfaceHolder holder, int format, int width,
        int height) {
    // TODO Auto-generated method stub

  }

  @Override
  public void surfaceCreated(SurfaceHolder holder) {

    Canvas c = holder.lockCanvas();
    onDraw(c);      
    holder.unlockCanvasAndPost(c);      
  }

  @Override
  public void surfaceDestroyed(SurfaceHolder holder) {
    // TODO Auto-generated method stub  

  } 

}

Resistor.java

public class Resistor extends View{

  private Path mSymbol;
  private Paint mPaint;

  private int mX;
  private int mY;

  //...Override Constructors...    
  public Resistor(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
  }

  public Resistor(Context context, int x, int y){
    super(context);
    mX = x;
    mY = y;
    init();
  }

  private void init() {
    mSymbol = new Path();
    mPaint = new Paint();

    mPaint.setAntiAlias(true);      
    mPaint.setStrokeWidth(2);
    mPaint.setColor(-7829368);
    mPaint.setStyle(Paint.Style.STROKE);

    //...Your code here to set up the path,
    //...allocate objects here, never in the drawing code.

    mSymbol.moveTo(0.0F, 0.0F);
    mSymbol.lineTo(0.0F, 50.0F);
    mSymbol.lineTo(16.666666F, 58.333332F);
    mSymbol.lineTo(-16.666666F, 75.0F);
    mSymbol.lineTo(16.666666F, 91.666664F);
    mSymbol.lineTo(-16.666666F, 108.33333F);
    mSymbol.lineTo(16.666666F, 124.99999F);
    mSymbol.lineTo(-16.666666F, 141.66666F);
    mSymbol.lineTo(0.0F, 150.0F);
    mSymbol.lineTo(0.0F, 200.0F);
    mSymbol.offset(mX, mY);

  }

  public void doDraw(Canvas canvas) {
    canvas.drawPath(mSymbol, mPaint);
  }

Answer 1

您应该使用ViewGroup代替SurfaceView。将Resistor - 视图作为子项添加到MyView，measure and layout them appropriately，ViewGroup将自动处理它们。

SurfaceView要求您在单独的帖子中进行绘图。您必须在surfaceCreated中启动该线程，并根据需要不断重绘视图。对于像你发布的那样的简单视图，在UI线程中进行绘图是完全可以接受的。不需要SurfaceView。

Answer 2

之前我没有使用过Surfaceview，但如果您在API中可以看到，SurfaceView类中没有名为“invalidate（）”的函数。

也许你可以设法以某种方式重复使用这条线：

holder.unlockCanvasAndPost(c);

为什么无效无效？

2 个答案: