Question

我有一个自定义视图，扩展RelativeLayout并将其用作ListView中的列表项。它基本上是一个左边有一个时髦角度的矩形。根据我在onTouchEvent中返回的内容，我最终可能处于两种可能的状态：

列表项将正确显示其按下状态并返回未按下状态，但不会将点击发送到ListView。
列表项将保持按下状态（并且无法退出）但是将点击完全发送到ListView。

我之前从未做过这种类型的自定义视图，但我真的很感激建议。我认为我错过了一些简单的事情，但是我现在花费了太多时间来继续这样做而没有提出问题！

以下是代码：

public class ListItemBackgroundView extends RelativeLayout {
    private final Path PATH = new Path();
    private final Paint BRUSH = new Paint(Paint.ANTI_ALIAS_FLAG);
    private static int mBackgroundColor = -1;
    private static int mPressedBackgroundColor = -1;
    private static int mAngleOffset = -1;

    private boolean isPressed;

    public ListItemBackgroundView(Context context) {
        super(context);
        setWillNotDraw(false);
    }

    public ListItemBackgroundView(Context context, AttributeSet attrs) {
        super(context, attrs);
        setWillNotDraw(false);
    }

    public ListItemBackgroundView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        setWillNotDraw(false);
    }

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

        final int w = canvas.getWidth();
        final int h = canvas.getHeight();

        if (mBackgroundColor == -1) {
            mBackgroundColor = getResources().getColor(R.color.color_1);
            mPressedBackgroundColor = getResources().getColor(R.color.color_2);
            mAngleOffset = getResources().getDimensionPixelSize(R.dimen.list_view_angle_offset);
        }

        PATH.moveTo(0, 0);
        PATH.lineTo(mAngleOffset, h * (0.35f));
        PATH.lineTo(0, h);
        PATH.lineTo(w, h);
        PATH.lineTo(w, 0);
        PATH.lineTo(0, 0);
        PATH.close();

        BRUSH.setStyle(Paint.Style.FILL);
        BRUSH.setColor(isPressed ? mPressedBackgroundColor : mBackgroundColor);

        canvas.drawPath(PATH, BRUSH);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        boolean result = super.onTouchEvent(event);
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                isPressed = true;
                result = false;
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                isPressed = false;
                result = true;
                invalidate();
                break;
        }
        return result;
    }
}

Answer 1

解决方案是使用StateListDrawable作为背景。

public class ListItemStateListDrawable extends StateListDrawable {
    private final int mBackgroundColor, mPressedBackgroundColor, mAngleOffset;
    private final Path PATH = new Path();
    private final Paint BRUSH_PRESSED = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint BRUSH = new Paint(Paint.ANTI_ALIAS_FLAG);
    private boolean isDrawn = false;
    private boolean isPressed = false;

    public ListItemStateListDrawable(int backgroundColor, int pressedBackgroundColor, int angleOffset) {
        this.mBackgroundColor = backgroundColor;
        this.mPressedBackgroundColor = pressedBackgroundColor;
        this.mAngleOffset = angleOffset;
    }

    @Override
    protected boolean onStateChange(int[] stateSet) {
        for(int st : stateSet){
            boolean pressed = st == android.R.attr.state_pressed;
            boolean not_pressed = st == android.R.attr.stateNotNeeded || st ==  -android.R.attr.state_pressed ||
                    st ==  android.R.attr.state_accelerated || st ==  android.R.attr.state_focused;
            if(pressed || not_pressed){
                isPressed = pressed;
                invalidateSelf();
                break;
            }
        }
        return super.onStateChange(stateSet);
    }

    @Override
    public void draw(Canvas canvas) {
        if(!isDrawn){
            final int w = canvas.getWidth();
            final int h = canvas.getHeight();

            PATH.moveTo(0, 0);
            PATH.lineTo(mAngleOffset, h * (0.35f));
            PATH.lineTo(0, h);
            PATH.lineTo(w, h);
            PATH.lineTo(w, 0);
            PATH.lineTo(0, 0);
            PATH.close();

            BRUSH.setStyle(Paint.Style.FILL);
            BRUSH.setColor(mBackgroundColor);
            BRUSH_PRESSED.setStyle(Paint.Style.FILL);
            BRUSH_PRESSED.setColor(mPressedBackgroundColor);

            canvas.drawPath(PATH, BRUSH);
            isDrawn = true;
        }else {
            canvas.drawPath(PATH, isPressed ? BRUSH_PRESSED : BRUSH);
        }
    }
}

Answer 2

使用StateListDrawable并通过addState添加状态是一种很好的标准方法，但你可以通过以下方式缩短它：

class MyStateListDrawable extends StateListDrawable {
    @Override
    protected boolean onStateChange(int[] stateSet) {
        invalidateSelf();
        return super.onStateChange(stateSet);
    }
    @Override
    public void draw(Canvas canvas) {
        int[] state = getState();
        Log.d(TAG, "draw " + StateSet.dump(getState()));
        // remove states you dont want or add you do
        if (isA(android.R.attr.state_pressed)) {
            Log.d(TAG, "draw state_pressed");
            canvas.drawColor(0xffff0000);
        } else
        if (isA(android.R.attr.state_focused)) {
            Log.d(TAG, "draw state_focused");
            canvas.drawColor(0xffff0000);
        } else
        if (isA(android.R.attr.state_selected)) {
            Log.d(TAG, "draw state_selected");
            canvas.drawColor(0xffffff00);
        } else {
            Log.d(TAG, "draw default state");
            canvas.drawColor(0xff0000ff);
        }
    }
    private boolean isA(int i) {
        int[] state = getState();
        for (int st : state) {
            if (st == i) {
                return true;
            }
        }
        return false;
    }
}

处理自定义视图的不同触摸状态

2 个答案: