本章节我们使用 Bitmap 开发一个截屏的小 demo

1. 创建一个 空的 Android 项目 cn.twle.android.BitmapCapture

2. 下载 /static/i/meimei.jpg 并保存到 res/drawable 目录下

3. 修改 activity_main.xml

   <?xml version="1.0" encoding="utf-8"?>
   <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent">
   
       <Button android:layout_width="wrap_content"
               android:layout_height="wrap_content"
               android:id="@+id/btn_capture"
               android:text="截屏" />
   
       <ImageView
           android:layout_width="match_parent"
           android:layout_height="match_parent"
           android:scaleType="center"
           android:src="@drawable/meimei" />
   </RelativeLayout>
   

4. 修改 MainActivity.java

   package cn.twle.android.bitmapcapture;
   
   import android.content.Intent;
   import android.graphics.Bitmap;
   import android.graphics.Canvas;
   import android.net.Uri;
   import android.os.Environment;
   import android.provider.MediaStore;
   import android.support.v7.app.AppCompatActivity;
   import android.os.Bundle;
   import android.view.View;
   import android.widget.Button;
   
   import java.io.ByteArrayOutputStream;
   import java.io.File;
   import java.io.FileNotFoundException;
   import java.io.FileOutputStream;
   import java.io.IOException;
   
   public class MainActivity extends AppCompatActivity {
       static ByteArrayOutputStream byteOut = null;
       private Bitmap bitmap = null;
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
   
           Button btn_capture = (Button) findViewById(R.id.btn_capture);
           btn_capture.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View v) {
                   captureScreen();
               }
           });
       }
   
       public void captureScreen() {
   
           Runnable action = new Runnable() {
               @Override
               public void run() {
                   final View contentView = getWindow().getDecorView();
                   try{
                       bitmap = Bitmap.createBitmap(contentView.getWidth(),
                               contentView.getHeight(), Bitmap.Config.ARGB_8888);
                       contentView.draw(new Canvas(bitmap));
                       ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
                       bitmap.compress(Bitmap.CompressFormat.JPEG, 100, byteOut);
                       saveCapture(bitmap);
                   }catch (Exception e){e.printStackTrace();}
                   finally {
                       try{
                           if (null != byteOut)
                               byteOut.close();
                           if (null != bitmap && !bitmap.isRecycled()) {
   //                            bitmap.recycle();
                               bitmap = null;
                           }
                       }catch (IOException e){e.printStackTrace();}
   
                   }
               }
           };
           try {
               action.run();
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   
       public void saveCapture(Bitmap bmp) {
   
           // 首先保存图片
           File appDir = new File(Environment.getExternalStorageDirectory(), "image");
           if (!appDir.exists()) {
               appDir.mkdir();
           }
           String fileName = System.currentTimeMillis() + ".jpg";
           File file = new File(appDir, fileName);
           try {
               FileOutputStream fos = new FileOutputStream(file);
               bmp.compress(Bitmap.CompressFormat.JPEG, 100, fos);
               fos.flush();
               fos.close();
           } catch (FileNotFoundException e) {
               e.printStackTrace();
           } catch (IOException e) {
               e.printStackTrace();
           }
   
           // 其次把文件插入到系统图库
           try {
               MediaStore.Images.Media.insertImage(getContentResolver(),
                       file.getAbsolutePath(), fileName, null);
           } catch (FileNotFoundException e) {
               e.printStackTrace();
           }
           // 最后通知图库更新
           sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" +file.getAbsolutePath())));
       }
   }
   

5. 修改 AndroidManifest.xml 添加读写 SD 卡权限

   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
   <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>