Question

我有一个自定义的Android视图，可以在屏幕上绘制波形。一个变量，cursorTask是一个TimerTask，它在startCursor结束执行和stopCursor被调用之间以某种方式变为null。我不知道这是如何发生的，因为它是私有的，所有的WaveView的startCursor函数都被调用。

public class WaveView extends View {
private Audio audio;

Paint wavePaint;
Paint progressPaint;
Paint barPaint;

private int progress;
private int maxProgress = 100;

private Timer timer;
private TimerTask cursorTask;

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

private void init(){
    timer = new Timer();

    wavePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    wavePaint.setColor(Color.BLUE);
    wavePaint.setStyle(Paint.Style.FILL);

    progressPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    progressPaint.setColor(Color.RED);
    progressPaint.setStrokeWidth(2.0f);

    barPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    barPaint.setColor(Color.CYAN);
    barPaint.setAlpha(100);
}

public void setAudio(Audio audio){
    this.audio = audio;
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if(audio != null && audio.waveValues != null && !audio.waveValues.isEmpty()){
        int w = canvas.getWidth();
        int h = canvas.getHeight();

        canvas.drawRect(new Rect(0, 0, w*audio.bars/Rhythm.maxBars, h), barPaint);

        Path path = new Path();
        path.moveTo(0,h);

        for(int i = 0; i < 100; i++){
            int x = i * w/100;

            if(audio.waveValues.size() <= i){
                path.lineTo(x, h);
                break;
            }

            int y = Math.round(h-audio.waveValues.get(i)*h);
            path.lineTo(x, y);
        }
        path.lineTo(w,h);

        canvas.drawPath(path, wavePaint);

        if(0 < progress){
            float x = progress*w*audio.bars/maxProgress/Rhythm.maxBars;
            canvas.drawLine(x, h, x, 0, progressPaint);
        }
    }
}

public void startCursor(int msLoopDuration){
    progress = 0;
    cursorTask = new TimerTask() {
        @Override
        public void run() {
            progress = (progress+1) % maxProgress;
            postInvalidate();
        }
    };
    timer.scheduleAtFixedRate(cursorTask, 0, msLoopDuration/maxProgress);
}

public void stopCursor(){
    cursorTask.cancel();
}
}

我通过在WaveView所在的适配器中的getView（）中的convertView中找到WaveView来调用它。

WaveView wave = (WaveView)convertView.findViewById(R.id.waveform);
wave.startCursor(Rhythm.msBarPeriod()*audio.bars);

非常感谢任何帮助。

Android View成员变量变为空

0 个答案: