Android传递Bitmap对象在两个Activity之间

时间：2020-10-17 10:42:51|栏目：Android代码|点击：次

通过内部存储方式实现了在两个Activity之间传递Bitmap对象以及其它支持串行化的Java对象，关键点有如下：

1． HTTP客户端下载图片，通过ImageView对象显示

2．把ImageView上的Bitmap对象从当前Activity传递到另外一个Activity中并显示出来

3．基于串行化传递Java对象数据

首先看我是怎么实现HTTP客户端下载图片，通过异步Task接口实现HTTP客户端下载图片并通过Handler来更新ImageView，代码如下：

package com.example.sharedemo; 
 
import java.io.IOException; 
import java.io.InputStream; 
 
import org.apache.http.HttpEntity; 
import org.apache.http.HttpResponse; 
import org.apache.http.HttpStatus; 
import org.apache.http.client.ClientProtocolException; 
import org.apache.http.client.HttpClient; 
import org.apache.http.client.methods.HttpGet; 
import org.apache.http.impl.client.DefaultHttpClient; 
 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.os.AsyncTask; 
import android.os.Handler; 
import android.os.Message; 
import android.util.Log; 
 
public class ImageLoadTask extends AsyncTask<String, Void, Bitmap> { 
  private Handler handler; 
 
  public ImageLoadTask(Handler handler) { 
    this.handler = handler; 
  } 
 
  protected void onPostExecute(Bitmap bitmap) { 
    Message msg = new Message(); 
    msg.obj = bitmap; 
    handler.sendMessage(msg); 
  } 
 
  @Override 
  protected Bitmap doInBackground(String... urls) { 
    Bitmap bitmap = null; 
    // create HTTP client 
    HttpClient httpclient = new DefaultHttpClient(); 
    try { 
      // GET request 
      Log.i("image-url", urls[0]); 
      HttpGet httpRequest = new HttpGet(urls[0]); 
      HttpResponse httpResponse = httpclient.execute(httpRequest); 
      if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { 
        // get entity from response 
        HttpEntity httpEntity = httpResponse.getEntity(); 
        // read stream 
        InputStream is = httpEntity.getContent(); 
        bitmap = BitmapFactory.decodeStream(is); 
        is.close(); 
        Log.i("image", "already get the image by url : " + urls[0]); 
      } 
 
    } catch (ClientProtocolException e) { 
      e.printStackTrace(); 
    } catch (IOException e) { 
      e.printStackTrace(); 
    } finally { 
      httpclient.getConnectionManager().shutdown(); 
    } 
    return bitmap; 
  } 
 
}

在当前的Activity中通过按钮上的事件响应实现切换View到对应的Activity中去，同时实现Java串行化数据传递。MainActivity的代码如下：

package com.example.sharedemo; 
 
import java.io.ByteArrayOutputStream; 
import java.io.FileOutputStream; 
 
import android.app.Activity; 
import android.content.Context; 
import android.content.Intent; 
import android.graphics.Bitmap; 
import android.graphics.Matrix; 
import android.graphics.drawable.BitmapDrawable; 
import android.os.Bundle; 
import android.os.Handler; 
import android.os.Message; 
import android.util.Log; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.ImageView; 
 
public class MainActivity extends Activity implements OnClickListener{ 
  public final static String SHARE_BITMAP_COMMAND = "share-image"; 
  public final static String SHARE_TEXT_DATA_COMMAND = "share-text-data"; 
  private Handler handler; 
 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    setupOnClickListener(); 
  } 
 
  private void setupOnClickListener() { 
    Button bitmapBtn = (Button)this.findViewById(R.id.bitmapShareBtn); 
    bitmapBtn.setTag(SHARE_BITMAP_COMMAND); 
    bitmapBtn.setOnClickListener(this); 
    Button textDataBtn = (Button)this.findViewById(R.id.mapShareBtn); 
    textDataBtn.setTag(SHARE_TEXT_DATA_COMMAND); 
    textDataBtn.setOnClickListener(this); 
    final ImageView imageView = (ImageView)this.findViewById(R.id.imageView1); 
     
    handler = new Handler() 
    { 
      public void handleMessage(Message msg) { 
        Bitmap bitmap = (Bitmap)msg.obj; 
        if(bitmap != null) 
        { 
          /* 
          // 为防止原始图片过大导致内存溢出，这里先缩小原图显示，然后释放原始Bitmap占用的内存 
          Bitmap smallBitmap = zoomBitmap(bitmap, bitmap.getWidth()/ 5, bitmap.getHeight() / 5); 
          // 释放资源 
          bitmap.recycle(); 
          // 显示图片 
          imageView.setImageBitmap(smallBitmap); 
          imageView.invalidate(); 
          */ 
          imageView.setImageBitmap(bitmap); 
        } 
      } 
    }; 
    ImageLoadTask task = new ImageLoadTask(handler); 
    task.execute("http://img.blog.csdn.net/20150607143208238"); 
  } 
   
  public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) { 
    int w = bitmap.getWidth(); 
    int h = bitmap.getHeight(); 
    Matrix matrix = new Matrix(); 
    float scaleWidth = ((float) width / w); 
    float scaleHeight = ((float) height / h); 
    matrix.postScale(scaleWidth, scaleHeight); // 不改变原来图像大小 
    Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true); 
    return newbmp; 
  } 
 
  @Override 
  public void onClick(View v) { 
    Object tag = v.getTag(); 
    Log.i("command", tag.toString()); 
    if(SHARE_BITMAP_COMMAND.equals(tag)) 
    { 
      Intent intent = new Intent(this.getApplicationContext(), ImageProcessActivity.class); 
      ImageView imageView = (ImageView)this.findViewById(R.id.imageView1); 
      Bitmap bitmap = ((BitmapDrawable)imageView.getDrawable()).getBitmap(); 
      intent.putExtra("selectedImage", bitmap); 
      intent.putExtra("name", "lena"); 
      intent.putExtra("description", "超级大美女"); 
      this.startActivity(intent);      
    } 
    else if(SHARE_TEXT_DATA_COMMAND.equals(tag)) 
    { 
      Intent intent = new Intent(this.getApplicationContext(), ImageProcessActivity.class); 
      ImageView imageView = (ImageView)this.findViewById(R.id.imageView1); 
      Bitmap bitmap = ((BitmapDrawable)imageView.getDrawable()).getBitmap(); 
      // save it first then pass URI 
      ImageInfoBean dto = new ImageInfoBean(); 
      String uri = createImageFromBitmap(bitmap); 
      dto.setDescription("超级大美女"); 
      dto.setName("lena"); 
      dto.setUri(uri); 
       
      intent.putExtra("tiger", dto); 
      this.startActivity(intent);  
    } 
  } 
   
  public String createImageFromBitmap(Bitmap bitmap) { 
    String fileName = "myImage"; 
    try { 
      ByteArrayOutputStream bytes = new ByteArrayOutputStream(); 
      bitmap.compress(Bitmap.CompressFormat.JPEG, 100, bytes); 
      FileOutputStream fo = openFileOutput(fileName, Context.MODE_PRIVATE); 
      fo.write(bytes.toByteArray()); 
      fo.close(); 
    } catch (Exception e) { 
      e.printStackTrace(); 
      fileName = null; 
    } 
    Log.i("fileName", fileName); 
    return fileName; 
  } 
}

对应另外一个Activity中实现读取与组装Bitmap对象显示的代码如下：

package com.example.sharedemo; 
 
import java.io.FileNotFoundException; 
 
import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.os.Bundle; 
import android.widget.ImageView; 
import android.widget.TextView; 
 
public class ImageProcessActivity extends Activity { 
 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.share_info); 
    backFillData(); 
  } 
 
  private void backFillData() { 
    Object obj = this.getIntent().getExtras().get("tiger"); 
    ImageView imageView = (ImageView)this.findViewById(R.id.imageView1); 
    TextView text1 = (TextView)this.findViewById(R.id.textView1); 
    TextView text2 = (TextView)this.findViewById(R.id.textView2); 
    try { 
      if(obj != null && obj instanceof ImageInfoBean) 
      { 
        ImageInfoBean dto = (ImageInfoBean)obj; 
        Bitmap bitmap = BitmapFactory.decodeStream(this.openFileInput(dto.getUri())); 
        imageView.setImageBitmap(bitmap); 
        imageView.invalidate(); // refresh 
         
        text1.setText("名称: " + dto.getName()); 
        text2.setText("描述: " + dto.getDescription()); 
        return; 
      } 
    } catch (FileNotFoundException e) { 
      e.printStackTrace(); 
    } 
     
    Bitmap bitmap = (Bitmap) this.getIntent().getParcelableExtra("selectedImage"); 
    String name = this.getIntent().getExtras().getString("name"); 
    String description = this.getIntent().getExtras().getString("description"); 
    if(bitmap != null) 
    { 
      imageView.setImageBitmap(bitmap); 
      imageView.invalidate(); // refresh 
    } 
    if(name != null) 
    { 
      text1.setText("名称: " + name); 
    } 
    if(description != null) 
    { 
      text2.setText("描述: " + description); 
    } 
  } 
 
}

对应的Java串行化对象类代码如下：

package com.example.sharedemo; 
 
import java.io.Serializable; 
 
public class ImageInfoBean implements Serializable { 
  /** 
   * 
   */ 
  private static final long serialVersionUID = 1L; 
 
  public String getName() { 
    return name; 
  } 
 
  public void setName(String name) { 
    this.name = name; 
  } 
 
  public String getDescription() { 
    return description; 
  } 
 
  public void setDescription(String description) { 
    this.description = description; 
  } 
 
  public String getUri() { 
    return uri; 
  } 
 
  public void setUri(String uri) { 
    this.uri = uri; 
  } 
 
  private String name; 
  private String description; 
  private String uri; 
 
}

最后声明：
别忘记在Manifest文件添加网络访问的权限

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

第一个按钮【传递图片】将会演示我遇到错误，第二按钮【传递文本数据】
将会演示正确的处理结果，显示如下：

以上就是本文的全部内容，希望对大家的学习有所帮助。

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