Android自定义视图没有重新绘制，虽然正在调用onDraw

Question

我有一个名为ArrowView自定义视图。

当这个视图是布局的一部分时，它是ArrayAdapter一部分，一切都很好。 （它被重新绘制为基础数据更改。）

当我使用相同的布局作为另一个Adapter的一部分时， ArrowView不会重新绘制。

我调试了它，发现onDraw 被调用，具有不同的rot值，当我预期它时 - 它只是屏幕没有更新。

我是否需要更改我的ArrowView正确重新绘制？

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

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（）将解决此问题。

这可以通过两种方式或更多方式完成!!!

在setter方法中调用runOnUi线程

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

或者只需在setter方法中调用postInvalidate() 。

Answer 2

如果调用onDraw（）但视图不自行更新，原因可能是在错误的线程上调用它。

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（）：通知附加的观察者基础数据已更改，反映数据集的任何视图都应刷新自身。