Android開發之加載圖片的方法

本文實例講述了Android開發之加載圖片的方法。分享給大家供大家參考。具體分析如下：

加載網絡上的圖片需要在manifest中配置訪問網絡的權限，如下：

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

如果不配置這個權限的話，會報錯：unknown host exception。

package com.example.loadimgfromweb; 
import java.io.InputStream; 
import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.view.Menu; 
import android.widget.ImageView; 
public class MainActivity extends Activity { 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    ImageView v = (ImageView) findViewById(R.id.imageView1); 
    String url = "http://minimg.hexun.com/i1.hexunimg.cn/2011-11-07/134970028_200x150.jpg"; 
    new DownLoadImage(v).execute(url); 
  } 
  @Override 
  public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.activity_main, menu); 
    return true; 
  } 
  public class DownLoadImage extends AsyncTask<String, Void, Bitmap> {
    ImageView imageView; 
    public DownLoadImage(ImageView imageView) { 
      this.imageView = imageView; 
    } 
    @Override 
    protected Bitmap doInBackground(String... urls) { 
      String url = urls[0]; 
      Bitmap tmpBitmap = null; 
      try { 
        InputStream is = new java.net.URL(url).openStream(); 
        tmpBitmap = BitmapFactory.decodeStream(is); 
      } catch (Exception e) { 
        e.printStackTrace(); 
      } 
      return tmpBitmap; 
    } 
    @Override 
    protected void onPostExecute(Bitmap result) { 
      imageView.setImageBitmap(result); 
    } 
  } 
}

如果是加載本地圖片的話，直接來：

ImageView v = (ImageView) findViewById(R.id.imageView1); 
    v.setImageResource(R.drawable.apic); 

在使用AsyncTask加載圖片的時候可以順便把圖片保存在本地：

@Override 
protected Bitmap doInBackground(String... urls) { 
  String url = urls[0]; 
  Bitmap tmpBitmap = null; 
  try { 
 InputStream is = new java.net.URL(url).openStream(); 
 URL u = new URL(url); 
 HttpURLConnection conn = (HttpURLConnection) u.openConnection();
 Bitmap bitmap = BitmapFactory.decodeStream(is); 
 // 判斷是否有內存卡 
 if (Environment.getExternalStorageState().equals( 
 Environment.MEDIA_MOUNTED)) {
   // 保存圖片到本地 
   File sdCardDir = Environment.getExternalStorageDirectory();
   String fileName = "a.jpg"; 
   String filePath = sdCardDir + "/" + fileName; 
   FileOutputStream fos = new FileOutputStream(filePath); 
   bitmap.compress(Bitmap.CompressFormat.PNG, 100, fos); 
 } 
 // 關閉流 
 is.close(); 
 conn.disconnect(); 
 return bitmap; 
  } catch (Exception e) { 
 e.printStackTrace(); 
  } 
  return tmpBitmap; 
} 

希望本文所述對大家的Android程序設計有所幫助。