怎么在自定义ImageView上Draw东西，然后获取为Bitmap?

public class MainActivity extends AppCompatActivity {

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    View view= View.inflate(this,R.layout.activity_main,null);
    //布局参数
    ViewGroup.LayoutParams layoutParams=new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
            ViewGroup.LayoutParams.WRAP_CONTENT);

    ImageView imageView=new ImageView(this);
    //设置布局参数
    imageView.setLayoutParams(layoutParams);
    imageView.setBackgroundColor(Color.RED);

    //把textview加入RelativeLayout中
    ((RelativeLayout)view).addView(imageView);

    //显示整个布局
    setContentView(view);
    setContentView(new SmileyView(this));




}

}

class SmileyView extends View {
private Paint mCirclePaint;
private float mCenterX;
private float mCenterY;
private float mRadius;

 public SmileyView(Context context) {
    this(context, null);
}

public SmileyView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public SmileyView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    initPaints();
}

private void initPaints() {
    mCirclePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    mCirclePaint.setStyle(Paint.Style.FILL);
    mCirclePaint.setColor(Color.YELLOW);
}

 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     int w = MeasureSpec.getSize(widthMeasureSpec);
     int h = MeasureSpec.getSize(heightMeasureSpec);

     int size = Math.min(w, h);
     setMeasuredDimension(size, size);
 }

 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
     mCenterX = w / 2f;
     mCenterY = h / 2f;
     mRadius = Math.min(w, h) / 2f;
 }

protected void onDraw(Canvas canvas) {
    canvas.drawCircle(mCenterX, mCenterY, mRadius, mCirclePaint);
    // draw eyes


}

}

上面这个代码如何修改为在ImageView上显示画的圆，然后把ImageView转化成Bitmap？麻烦具体点，我小白

之前写过一个类似的，不过没自定义控件，在画布上画的文字，再把控件内容覆盖到上面，跟你这反过来就行了，你可以参考一下：

//截取scrollview的屏幕
public static Bitmap getScrollViewBitmap(NestedScrollView scrollView) {
        int h = 0;
        Bitmap bitmap;
        for (int i = 0; i < scrollView.getChildCount(); i++) {
                h += scrollView.getChildAt(i).getHeight();
        }
        // 创建相应大小的bitmap
        bitmap = Bitmap.createBitmap(scrollView.getMeasuredWidth(), h,
                        Bitmap.Config.ARGB_4444);
        final Canvas canvas = new Canvas(bitmap);
        canvas.drawColor(Color.parseColor("#FFFFFF"));
        drawTextToBitmap(scrollView.getContext(), canvas, scrollView.getMeasuredWidth(), h);
        scrollView.draw(canvas);
        return bitmap;
}

// 给图片添加水印
public static void drawTextToBitmap(Context context, Canvas canvas, int width, int height) {
        String logo = "戚大爷";
        Paint paint = new Paint();
        paint.setColor(SkinManager.getInstance().getResourceManager().getColor("future_text_bg"));
        paint.setAlpha(80);
        paint.setAntiAlias(true);
        paint.setTextSize((float) DensityUtil.dip2px(context, 30));
        canvas.save();
        canvas.rotate(-30);
        float textWidth = paint.measureText(logo);
        int index = 0;
        for (int positionY = -DensityUtil.dip2px(context, 30); positionY <= height; positionY += DensityUtil.dip2px(context, 80)) {
                float fromX = -0.75f * height + (index++ % 2) * textWidth;
                for (float positionX = fromX; positionX < width; positionX += textWidth * 2) {
                        canvas.drawText(logo, positionX, positionY, paint);
                }
        }
        canvas.restore();
}

希望能够帮助到你！

一般都是 在自定义View上面画东西，然后保存成bitmap

//generate picture
private Bitmap convertViewToBitmap(View view){
    Bitmap bitmap = Bitmap.createBitmap(view.getLayoutParams().width, view.getLayoutParams().height,
            Bitmap.Config.RGB_565);

    Log.i("blb", "-------convert view's height, :" + view.getLayoutParams().height + ", width: " + view.getLayoutParams().width + ", getHeight:" + view.getHeight());
    //利用bitmap生成画布
    Canvas canvas = new Canvas(bitmap);

    //把view中的内容绘制在画布上
    view.draw(canvas);

    return bitmap;
}

    然后这样就生成bitmap了。

还是不知道如何获取到画出来的界面。

public static Bitmap convertViewToBitmap(View view){
view.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
view.buildDrawingCache();
Bitmap bitmap = view.getDrawingCache();

    return bitmap;
}

public class MainActivity extends AppCompatActivity {
ImageView imageView; Bitmap bitmap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
imageView=(ImageView) this.findViewById(R.id.imageView);
View view= View.inflate(this,R.layout.activity_main,null);

    //布局参数
    ViewGroup.LayoutParams layoutParams=new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
            ViewGroup.LayoutParams.WRAP_CONTENT);

    setContentView(new SmileyView(this,null));
    bitmap= convertViewToBitmap(view);

    if(bitmap!=null){
        Log.d("xg","not null");
       //imageView.setImageBitmap(bitmap);

    }else {
        Log.d("xg","null,null, null");
    }
    //调用保存方法
    saveBitmap();
}
//吧view转化为bitmap
public static Bitmap convertViewToBitmap(View view){
    view.measure(View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED), View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
    view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
    Log.i("xg",view.getMeasuredWidth()+"--"+view.getMeasuredHeight());
    view.setDrawingCacheEnabled(true);
    view.buildDrawingCache();
    Bitmap bitmap = view.getDrawingCache();
    view.destroyDrawingCache();
    return bitmap;
}


public void saveBitmap() {


    String state= Environment.getExternalStorageState();
    File file;

    try {
        if(Environment.MEDIA_MOUNTED.equals(state)){
            // 保存图片到SD卡上
            file = Environment.getExternalStorageDirectory();
        }else{
            file =getFilesDir();
        }

        FileOutputStream stream = new FileOutputStream(file.getAbsolutePath()+"/sign/"+System.currentTimeMillis()+".png");
        bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
        Toast.makeText(MainActivity.this, "保存图片成功", 0).show();


        stream.flush();
        stream.close();

    } catch (Exception e) {
        Toast.makeText(MainActivity.this, "保存图片失败", 1).show();
        e.printStackTrace();
    }


}

}

class SmileyView extends View {
private Paint mCirclePaint;
private float mCenterX;
private float mCenterY;
private float mRadius;

public SmileyView(Context context) {
    this(context, null);
}

public SmileyView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public SmileyView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    initPaints();
}

private void initPaints() {
    mCirclePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    mCirclePaint.setStyle(Paint.Style.FILL);
    mCirclePaint.setColor(Color.YELLOW);
}

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    int w = MeasureSpec.getSize(widthMeasureSpec);
    int h = MeasureSpec.getSize(heightMeasureSpec);

    int size = Math.min(w, h);
    setMeasuredDimension(size, size);
}

protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    mCenterX = w / 2f;
    mCenterY = h / 2f;
    mRadius = Math.min(w, h) / 2f;
}

protected void onDraw(Canvas canvas) {
    canvas.drawCircle(mCenterX, mCenterY, mRadius, mCirclePaint);
    // draw eyes


}

}
bitmap都已经不为空了，还是无法保存，保存代码试过的，也没问题，读写权限，包括手机上的储存权限也是开的。