两种方式实现圆形图片

一，自定义drawable

利用画笔方法setShader（）。

自定义Drawable 代码

public class MyDrawable extends Drawable {
private Paint mPaint;
private Bitmap bitmap;

public MyDrawable(Bitmap bitmap) {
this.bitmap = bitmap;
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
BitmapShader bs = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
mPaint.setShader(bs);
}

@Override
public void draw(Canvas canvas) {
canvas.drawCircle(bitmap.getWidth() / 2, bitmap.getHeight() / 2, Math.min(bitmap.getWidth() / 2, bitmap.getHeight() / 2), mPaint);
}

@Override
public void setAlpha(int alpha) {

}

@Override
public void setColorFilter(ColorFilter colorFilter) {

}

@Override
public int getOpacity() {
return 0;
}

@Override
public int getIntrinsicWidth() {
return bitmap.getWidth();
}

@Override
public int getIntrinsicHeight() {
return bitmap.getHeight();
}
}

利用BitmapShader 着色画笔来实现，相当于画笔绘制的区域利用图片相应的区域来代替。

二，自定义View

利用画笔方法setXfermode()。

首先是google给出的官方图谱



奈何被这张图坑了好久，发现这图不对。

正确的应该是：



自定义View代码

public class MyView extends View {
private Paint mPaint;
private Bitmap mBitmap;

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

public MyView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public MyView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.MyView);
int indexCount = ta.getIndexCount();
Log.e("ethan","indexCount=="+indexCount);
for (int i = 0; i <= indexCount; i++) {
int index = ta.getIndex(i);
switch (index) {
case R.styleable.MyView_map:
BitmapDrawable bitmapDrawable = (BitmapDrawable) ta.getDrawable(index);
Log.e("ethan","dr=="+bitmapDrawable);
mBitmap = bitmapDrawable.getBitmap();
break;
}
}
ta.recycle();
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
}
@Override
protected void onDraw(Canvas canvas) {
Rect r=new Rect(0,0,getWidth(),getHeight());
int width = getWidth() / 2;
int height = getHeight() / 2;
int i = canvas.saveLayer(0, 0, getWidth(), getHeight(), mPaint, Canvas.ALL_SAVE_FLAG);
canvas.drawCircle(width, height, Math.min(width, height), mPaint);
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(mBitmap, null, r, mPaint);
canvas.restoreToCount(i);
}
}

ondraw()注意调用canvas.saveLayer和canvas.restoreToCount(i)。否则需要新建一张bitmap的画布，然后调用canvas的drawBitmap。

MainActivity代码

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

ImageView iv= (ImageView) findViewById(R.id.imageview);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.t);
iv.setImageDrawable(new MyDrawable(bitmap));

}
}

Xml：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:ethan="http://schemas.android.com/apk/res-auto"
android:id="@+id/layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:animateLayoutChanges="true"
android:orientation="vertical">

<ImageView
android:id="@+id/imageview"
android:layout_width="150dp"
android:layout_height="150dp"
android:src="@mipmap/t" />

<com.example.administrator.androidtraining.utils.MyView
ethan:map="@mipmap/t"
android:layout_width="150dp"
android:layout_height="150dp" />

</LinearLayout>

attars

<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="MyView">
<attr name="map" format="reference" />
</declare-styleable>
</resources>

效果图，上面为自定义drawable