Android上在两个Activity之间传递Bit地图对象

Android上在两个Activity之间传递Bitmap对象

因为我做Android应用的时间不长，所以当我第一次在android之间传递Bitmap对象的时候我直接用了Intent.putExtra的方法实现了，当时我选择的是一张图像的ROI区域，所以工作的很好，但是当我尝试将整个图片做为Bitmap对象传到另外一个Activity中的时候总是得到一个错误fatal bind error我当时很郁闷了好久，后来google才发现是这样传递Bitmap对象的方式不对，Activity之间传递Bitmap有大小限制，而且这个大小限制很小，512x512的图片肯定会得到我上述的这个错误，于是我想到了先保存到SD卡上然后传递路径的方法，但是SD卡属于外部存储，可能不是特别方便，后来看到有人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，我觉得很好，所以就写了这篇博客。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);		}	}}

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;}

别忘记在Manifest文件添加网络访问的权限

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

将会演示正确的处理结果，显示如下：