android加載網絡圖片並保留緩存，隨時點擊打開

今天工作需要寫了一個保留網絡圖片緩存的類，和大家分享一下

其實實現原理很簡單，也就是從網上下載圖片數據，一邊將數據轉成drawable並加載到指定的imageview

一邊保存成download_image.jpg，在點擊imageview時候用intent將圖片打開

我將處理圖片的過程寫成了類

package com.example.downloadandopenimage;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.content.Context;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageView;
import android.widget.ProgressBar;

public class LoadAndSaveImage {
	ImageView view;
	Context mContext;

	public LoadAndSaveImage() {
		// TODO Auto-generated constructor stub
	}

	public LoadAndSaveImage(Context context, String str, ImageView view) {
		// TODO Auto-generated constructor stub
		this.view = view;
		mContext = context;
		new Load_and_save_image().execute(str);
	}

	void release() {
		File file = new File("file://"
				+ Environment.getExternalStorageDirectory().toString()
				+ "/download_image.jpg");
		if (file.exists()) {
			boolean deleted = file.delete();
		}
	}

	class Load_and_save_image extends AsyncTask<String, Void, Void> {

		@Override
		protected Void doInBackground(String... sUrl) {
			// TODO Auto-generated method stub
			InputStream input = null;
			OutputStream output = null;
			HttpURLConnection connection = null;
			try {
				URL url = new URL(sUrl[0]);
				connection = (HttpURLConnection) url.openConnection();
				connection.connect();

				// download the file
				input = connection.getInputStream();
				File checker = new File("file://"
						+ Environment.getExternalStorageDirectory().toString()
						+ "/download_image.jpg");
				if (checker.exists()) {
					boolean deleted = checker.delete();
				}
				output = new FileOutputStream(Environment
						.getExternalStorageDirectory().toString()
						+ "/download_image.jpg");

				byte data[] = new byte[4096];
				int count;
				while ((count = input.read(data)) != -1) {
					output.write(data, 0, count);
				}
			} catch (Exception e) {
			} finally {
				try {
					if (input != null)
						input.close();
					if (output != null) {
						output.close();
					}
				} catch (IOException ignored) {
				}

				if (connection != null)
					connection.disconnect();
			}
			return null;
		}

		protected void onPostExecute(Void result) {
			Drawable d = Drawable.createFromPath(Environment
					.getExternalStorageDirectory().toString()
					+ "/download_image.jpg");
			view.setImageDrawable(d);
			view.setOnClickListener(new OnClickListener() {

				@Override
				public void onClick(View v) {
					// TODO Auto-generated method stub
					Intent intent = new Intent();
					intent.setAction(Intent.ACTION_VIEW);
					intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
					intent.setDataAndType(Uri.parse("file://"
							+ Environment.getExternalStorageDirectory()
									.toString() + "/download_image.jpg"),
							"image/*");
					mContext.startActivity(intent);
				}
			});
		};
	}

}

只要在activity中這樣寫：

	image = (ImageView) findViewById(R.id.image);
		new LoadAndSaveImage(getApplicationContext(), "http://toolongdidntread.com/wp-content/uploads/2011/06/upload.png", image);

三個參數分別是content，圖片的url，你要加載的imageview

BTW，由於這裏設置的儲存的jpg文件名字是固定的，加載多張圖片時請用隨機數或者自行命名

源碼在這裏：→http://download.csdn.net/detail/edwardwayne/8621419