1 问题
实现任意view经过自定义带4圆角或者2圆角的效果
2 原理
1) 实现view 4圆角
我们只需要把左边的图嵌入到右边里面去，最终显示左边的图就行。
2) 实现view上2圆角
我们只需要把左边的图嵌入到右边里面去，最终显示左边的图就行。
安卓源码里面有这样的类
package android.graphics;
/**
* <p>Specialized implementation of {@link Paint}'s
* {@link Paint#setXfermode(Xfermode) transfer mode}. Refer to the
* documentation of the {@link PorterDuff.Mode} enum for more
* information on the available alpha compositing and blending modes.</p>
*
*/
public class PorterDuffXfermode extends Xfermode {
/**
* Create an xfermode that uses the specified porter-duff mode.
*
* @param mode The porter-duff mode that is applied
*/
public PorterDuffXfermode(PorterDuff.Mode mode) {
porterDuffMode = mode.nativeInt;
}
}
然后我们看下点击mode进去看下
/**
* @hide
*/
public static Mode intToMode(int val) {
switch (val) {
default:
case 0: return Mode.CLEAR;
case 1: return Mode.SRC;
case 2: return Mode.DST;
case 3: return Mode.SRC_OVER;
case 4: return Mode.DST_OVER;
case 5: return Mode.SRC_IN;
case 6: return Mode.DST_IN;
case 7: return Mode.SRC_OUT;
case 8: return Mode.DST_OUT;
case 9: return Mode.SRC_ATOP;
case 10: return Mode.DST_ATOP;
case 11: return Mode.XOR;
case 16: return Mode.DARKEN;
case 17: return Mode.LIGHTEN;
case 13: return Mode.MULTIPLY;
case 14: return Mode.SCREEN;
case 12: return Mode.ADD;
case 15: return Mode.OVERLAY;
}
}什么意思呢？
应该可以看得懂，这里每个图片显示的效果是最终的效果，然后很明显，我们这里需要的是SrcIn效果，我们要把左图的效果嵌套到右图里面去。
3 代码实现
1）MyTextView.java文件如下
package com.onemt.sdk.circle;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.util.AttributeSet;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.widget.AppCompatTextView;
public class MyTextView extends AppCompatTextView {
private final RectF roundRect = new RectF();
private final Paint desPaint = new Paint();
private final Paint srcPaint = new Paint();
private float mRadius = 10;
private boolean isChange = false;
public MyTextView(@NonNull Context context) {
super(context);
init();
}
public MyTextView(@NonNull Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init();
}
public MyTextView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
public void change(boolean isChange) {
this.isChange = isChange;
invalidate();
}
public void init() {
desPaint.setAntiAlias(true);//设置抗锯齿
desPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
srcPaint.setAntiAlias(true);
float density = getResources().getDisplayMetrics().density;
mRadius *= density;
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
int width = getWidth();
int height = getHeight();
roundRect.set(0, 0, width, height);
}
@Override
public void draw(Canvas canvas) {
//保存最原始的roundRect
canvas.saveLayer(roundRect, srcPaint, Canvas.ALL_SAVE_FLAG);
if (isChange) {
//保存去掉头部2圆角的roundRect(实际就是保留底部的2个圆角)
canvas.drawRect(roundRect.left, roundRect.top + 100, roundRect.right, roundRect.bottom, srcPaint);
//保存去掉底部2圆角的roundRect(实际就是保留顶部的2个圆角)
// canvas.drawRect(roundRect.left, roundRect.top, roundRect.right, roundRect.bottom / 2, srcPaint);
}
//保存掉头部2圆角的roundRect
canvas.drawRoundRect(roundRect, mRadius, mRadius, srcPaint);
//保存叠加后的内容
canvas.saveLayer(roundRect, desPaint, Canvas.ALL_SAVE_FLAG);
super.draw(canvas);
//清空所有的图像矩阵修改状态
canvas.restore();
}
}
如果你看不懂这个函数drawRoundRect，请看下我的这篇博客介绍 Android之Canvas的drawRoundRect()
2）MainActivity.java文件如下
package com.onemt.sdk.circle;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
public class MainActivity extends AppCompatActivity {
public MyTextView myTextView;
public boolean isChange = true;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myTextView = findViewById(R.id.my_textview);
myTextView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (isChange) {
myTextView.change(true);
isChange = false;
} else {
myTextView.change(false);
isChange = true;
}
}
});
}
}
3）activity_main.xml文件如下
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.onemt.sdk.circle.MyTextView
android:id="@+id/my_textview"
android:layout_width="100dp"
android:layout_height="100dp"
android:background="@color/colorAccent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>4 效果
初始进来如下效果，4圆角效果
然后我们点击图片切换效果如下，上2圆角效果
