如何在Android的圆形ImageView上添加阴影和边框？

此示例演示如何在Android的圆形ImageView上添加阴影和边框。

步骤 1 - 在Android Studio中创建一个新项目，转到文件 ⇒ 新建项目，并填写所有必需的详细信息以创建新项目。

步骤 2 - 将以下代码添加到res/layout/activity_main.xml。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
   android:id="@+id/rl"
   android:padding="16dp"
   tools:context=".MainActivity">
   <ImageView
      android:id="@+id/iv"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"/>
   <Button
      android:id="@+id/btn_circular"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Circular It"
      android:layout_alignParentBottom="true"
      android:layout_alignParentRight="true"/>
</RelativeLayout>

步骤 3 - 将以下代码添加到src/MainActivity.java。

package com.app.sample;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.drawable.RoundedBitmapDrawable;
import androidx.core.graphics.drawable.RoundedBitmapDrawableFactory;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.os.Bundle;
public class MainActivity extends AppCompatActivity {
   private Context mContext;
   private Resources mResources;
   private RelativeLayout mRelativeLayout;
   private Button mBTNCircular;
   private ImageView mImageView;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      mContext = getApplicationContext();
      mResources = getResources();
      mRelativeLayout = (RelativeLayout) findViewById(R.id.rl);
      mImageView = (ImageView) findViewById(R.id.iv);
      mBTNCircular = (Button) findViewById(R.id.btn_circular);
      final Bitmap srcBitmap = BitmapFactory.decodeResource(mResources, R.drawable.flower);
      mImageView.setImageBitmap(srcBitmap);
      mBTNCircular.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View view) {
            Paint paint = new Paint();
            int srcBitmapWidth = srcBitmap.getWidth();
            int srcBitmapHeight = srcBitmap.getHeight();
            int borderWidth = 25;
            int shadowWidth = 10;
            int dstBitmapWidth = Math.min(srcBitmapWidth,srcBitmapHeight)+borderWidth*2;
            Bitmap dstBitmap = Bitmap.createBitmap(dstBitmapWidth,dstBitmapWidth, Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(dstBitmap);
            canvas.drawColor(Color.WHITE);
            canvas.drawBitmap(srcBitmap, (dstBitmapWidth - srcBitmapWidth) / 2, (dstBitmapWidth - srcBitmapHeight) / 2, null);
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(borderWidth * 2);
            paint.setColor(Color.WHITE);
            canvas.drawCircle(canvas.getWidth() / 2, canvas.getHeight() / 2, canvas.getWidth() / 2, paint);
            paint.setColor(Color.LTGRAY);
            paint.setStrokeWidth(shadowWidth);
            canvas.drawCircle(canvas.getWidth()/2,canvas.getHeight()/2,canvas.getWidth()/2,paint);
            RoundedBitmapDrawable roundedBitmapDrawable = RoundedBitmapDrawableFactory.create(mResources, dstBitmap);
            roundedBitmapDrawable.setCircular(true);
            roundedBitmapDrawable.setAntiAlias(true);
            mImageView.setImageDrawable(roundedBitmapDrawable);
         }
      });
   }
}

步骤 4 - 将以下代码添加到Manifests/AndroidManifest.xml。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.app.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
         <activity android:name=".MainActivity">
            <intent-filter>
               <action android:name="android.intent.action.MAIN" />
               <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
         </activity>
   </application>
</manifest>

让我们尝试运行您的应用程序。我假设您已将您的实际Android手机设备连接到您的电脑。要从Android Studio运行应用程序，请打开您的项目活动文件之一，然后单击运行工具栏中的图标。选择您的手机设备作为选项，然后检查您的手机设备，它将显示您的默认屏幕 -