Android 自定义视图未重绘，但正在调用 onDraw

Question

我有一个名为 ArrowView 的自定义视图。

当此视图是 ArrayAdapter 布局的一部分时，一切都很好。（它会随着基础数据的变化而重新绘制。）

当我将相同的布局用作另一个 Adapter 的一部分时，ArrowView 不会重新绘制。

我调试了它，发现 onDraw 被调用了 ，rot 的值不同，而我期望它是 - 它是只是屏幕没有更新。

我是否需要更改我的 ArrowView 以使其正确重绘？

public class ArrowView extends View {

    private Path path;
    public final Paint paint;
    public final Paint circlePaint;
    private float rot = 30;
    private float length = 0.5f;
    private float width = 1.0f;
    public final static int SIZE = 96;
    private float size = SIZE;
    private float xOff;
    private float yOff;

    public ArrowView(Context context, AttributeSet attrs) {
        super(context, attrs);

        path = new Path();
        path.moveTo( 0.0f,  -0.5f);
        path.lineTo( 0.5f,   0.0f);
        path.lineTo( 0.25f,  0.0f);
        path.lineTo( 0.25f,  0.5f);
        path.lineTo(-0.25f,  0.5f);
        path.lineTo(-0.25f,  0.0f);
        path.lineTo(-0.5f,   0.0f);
        path.close();

        paint = new Paint();
        paint.setARGB(150, 0, 150, 0);

        circlePaint = new Paint();
        circlePaint.setARGB(50, 150, 150, 150);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.save();
        canvas.translate(xOff, yOff);
        canvas.scale(size, size);
        canvas.save();
        canvas.translate(0.5f, 0.5f);
        canvas.drawCircle(-0.0f, -0.0f, 0.5f, circlePaint);
        canvas.save();
        canvas.rotate(rot, 0.0f, 0.0f);
        canvas.save();
        canvas.scale(width, length);
        canvas.drawPath(path, paint);
        canvas.restore();
        canvas.restore();
        canvas.restore();
        canvas.restore();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

        //Get the width measurement
        int widthSize = getMeasurement(widthMeasureSpec,
                SIZE);

        //Get the height measurement
        int heightSize = getMeasurement(heightMeasureSpec,
                SIZE);

        size = min(widthSize, heightSize) * 0.9f;
        xOff = 0.0f;
        yOff = 0.05f * size;

        //MUST call this to store the measurements
        setMeasuredDimension(widthSize, heightSize);
    }

    public static int getMeasurement(int measureSpec, int contentSize) {
        int specMode = View.MeasureSpec.getMode(measureSpec);
        int specSize = View.MeasureSpec.getSize(measureSpec);
        int resultSize = 0;
        switch (specMode) {
            case View.MeasureSpec.UNSPECIFIED:
                //Big as we want to be
                resultSize = contentSize;
                break;
            case View.MeasureSpec.AT_MOST:
                //Big as we want to be, up to the spec
                resultSize = min(contentSize, specSize);
                break;
            case View.MeasureSpec.EXACTLY:
                //Must be the spec size
                resultSize = specSize;
                break;
        }

        return resultSize;
    }

    public void setLength(float length) {
        this.length = length;
        invalidate();
    }

    public float getLength() {
        return length;
    }

    public void setWidth(float width) {
        this.width = width;
        invalidate();
    }

    public void setRot(float rot) {
        this.rot = rot;
        invalidate();
    }

}

Answer 1

如果调用了 onDraw() 但视图没有自行更新，原因可能是在错误的线程上调用了它。

在您的适配器中，请确保从 UI 线程

处理您的视图

 getActivity().runOnUiThread(new Runnable() {
    @Override
    public void run() {
    mAdapter.updateRot(newRot);
 });

 public void updateRot(double newRot){
     arrowView.setRot(newRot);
     notifyDataSetChanged();
 }

从适配器使用notifyDataSetChanged()刷新视图

notifyDataSetChanged(): Notifies the attached observers that the underlying data has been changed and any View reflecting the data set should refresh itself.

Answer 2

当我想从非ui线程和片段更新视图时，我也遇到了同样的问题； invalidate() 方法不更新视图。所以根据 sdk 参考

http://developer.android.com/intl/es/reference/android/view/View.html postInvalidate() 将解决问题。

这可以通过两种或更多方式完成！！！

在setter方法中调用runOnUi线程

runOnUiThread(new Runnable() {
    public void run() {
     this.length = length;
    this.invalidate();
    }
});

或者在setter方法中调用postInvalidate()。

Android 自定义视图未重绘，但正在调用 onDraw

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