1,下载ImageLoad.jar包放入项目libs文件夹中,并点击右键—>add as Library
2,首先记得在Manifest.xml注册权限(注:6.0以后的版本要在代码中动态注册权限)
- <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
- <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
 
3,布局文件,一个ImageView用来显示加载的图片,Button点击后进入系统相册选取图片
- <?xml version="1.0" encoding="utf-8"?>
- <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
-     xmlns:tools="http://schemas.android.com/tools"
-     android:layout_width="match_parent"
-     android:layout_height="match_parent"
-     android:orientation="vertical"
-     tools:context="com.zcn.demo.loadgallerypicture.MainActivity">
-  
-     <ImageView
-         android:id="@+id/pic"
-         android:src="@mipmap/ic_launcher"
-         android:layout_width="120dp"
-         android:layout_height="120dp" />
-     <Button
-         android:id="@+id/btn"
-         android:layout_width="match_parent"
-         android:layout_height="48dp"
-         android:layout_gravity="bottom"
-         android:text="button"/>
- </LinearLayout>
 
4,.java文件
- package com.zcn.demo.loadgallerypicture;
-  
- import android.Manifest;
- import android.annotation.TargetApi;
- import android.app.Activity;
- import android.content.Intent;
- import android.content.pm.PackageManager;
- import android.database.Cursor;
- import android.graphics.Bitmap;
- import android.graphics.BitmapFactory;
- import android.net.Uri;
- import android.os.Build;
- import android.support.v4.content.ContextCompat;
- import android.support.v7.app.AppCompatActivity;
- import android.os.Bundle;
- import android.util.Log;
- import android.view.View;
- import android.widget.Button;
- import android.widget.ImageView;
-  
- import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
- import com.nostra13.universalimageloader.core.DisplayImageOptions;
- import com.nostra13.universalimageloader.core.ImageLoader;
- import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
- import com.nostra13.universalimageloader.core.assist.QueueProcessingType;
-  
- import java.io.File;
- import java.io.FileOutputStream;
- import java.io.IOException;
-  
- public class MainActivity extends AppCompatActivity {
-     private static int WRITE_SD_CODE = 1;
-     private static int READ_SD_CODE = 2;
-     private static String TAG = "ZCN_MainActivity";
-     private ImageView image;
-     private Button btn;
-  
-     private String pic_path;
-     private DisplayImageOptions options;
-  
-     @Override
-     protected void onCreate(Bundle savedInstanceState) {
-         super.onCreate(savedInstanceState);
-         setContentView(R.layout.activity_main);
-         image = (ImageView)findViewById(R.id.pic);
-         btn = (Button)findViewById(R.id.btn);
-         btn.setOnClickListener(new View.OnClickListener() {
-             @Override
-             public void onClick(View view) {
-                 requestPermission();
-             }
-         });
-     }
-  
-     //android 6.0 以上版本要手动要求权限
-     @TargetApi(Build.VERSION_CODES.M)
-     private void requestPermission() {
-         if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
-             this.requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},READ_SD_CODE);
-         }else {
-             Log.v(TAG, "6.0一下版本直接打开相册....");
-             Intent intent = new Intent(Intent.ACTION_PICK,
-                     android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
-             startActivityForResult(intent, ActivityRequestCode.SHOW_MAP_DEPOT);
-         }
-     }
-  
-     //权限选择结果接收
-     @Override
-     public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
-         super.onRequestPermissionsResult(requestCode, permissions, grantResults);
-         if (requestCode == READ_SD_CODE) {
-             if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
-                 // 用户授予了此权限
-                 // 调用android自带的图库
-                 Intent intent = new Intent(Intent.ACTION_PICK,
-                         android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
-                 startActivityForResult(intent, ActivityRequestCode.SHOW_MAP_DEPOT);
-             } else {
-                 // 用户拒绝了此权限
-             }
-         }
-     }
-  
-     public interface ActivityRequestCode {
-         public static final int SHOW_MAP_DEPOT = 1; //显示Android自带图库,用于选择用户自己的图片
-     }
-  
-     public void onActivityResult(int requestCode, int resultCode, Intent data) {
-         super.onActivityResult(requestCode, resultCode, data);
-         if (data != null) {
-             if (requestCode == ActivityRequestCode.SHOW_MAP_DEPOT
-                     && resultCode == Activity.RESULT_OK)
-                 showPic(resultCode,data);
-         }
-     }
-  
-     // 调用android自带图库,显示选中的图片
-     private void showPic(int resultCode,Intent data) {
-         if(resultCode== Activity.RESULT_OK) {
-             if (data!=null) {
-                 Uri uri = data.getData();
-                 Log.v(TAG, "uri = "+uri);
-                 if (uri!=null) {
-                     Cursor cursor = getContentResolver().query(uri, null, null, null, null);
-                     //选择的就只是一张图片,所以cursor只有一条记录
-                     if (cursor != null) {
-                         if (cursor.moveToFirst()) {
-                             String path = cursor.getString(cursor.getColumnIndex("_data"));//获取相册路径字段
-                             Log.v(TAG, "打开相册获取的图片sd卡路径:" + path);
-                             File file = new File(path);
-                             initOptions();
-                             ImageLoader.getInstance().displayImage(uri.toString(), image,options);
-                             //保存图片到data/data/files文件夹下
-                             BitmapFactory.Options options = new BitmapFactory.Options();
-                             options.inJustDecodeBounds = true;
-                             Bitmap bitmap = BitmapFactory.decodeFile(path, options);
-                             File f = getFileStreamPath("ic_mine_head_portrait.jpg");
-                             Log.d(TAG, "File path :" + file.getParentFile());
-                             if (!f.exists()) {
-                                 Log.d(TAG, "文件不存在");
-                                 FileOutputStream out = null;
-                                 try{
-                                     f.createNewFile();
-                                     out = new FileOutputStream(f);
-                                     if(bitmap.compress(Bitmap.CompressFormat.PNG, 90, out))
-                                     {
-                                         out.flush();
-                                         out.close();
-                                     }
-                                 } catch (IOException e) {
-                                     e.printStackTrace();
-                                 }finally {
-                                     try {
-                                         out.close();
-                                     } catch (IOException e) {
-                                         e.printStackTrace();
-                                     }
-                                 }
-                             }
-                         }
-                     }
-                 }
-             }
-         }else{
-             Log.d(TAG,"放弃从相册选择");
-         }
-     }
-  
-     private void initOptions(){
-         options = new DisplayImageOptions.Builder().showStubImage(R.mipmap.ic_main_ad_stub) // 设置图片下载期间显示的图片
-                 .showImageForEmptyUri(R.mipmap.ic_main_ad_empty) // 设置图片Uri为空或是错误的时候显示的图片
-                 .showImageOnFail(R.mipmap.ic_main_ad_error) // 设置图片加载或解码过程中发生错误显示的图片
-                 .cacheInMemory(true) // 设置下载的图片是否缓存在内存中
-                 .cacheOnDisc(true) // 设置下载的图片是否缓存在SD卡中
-                 // .displayer(new RoundedBitmapDisplayer(20)) // 设置成圆角图片
-                 .build(); // 创建配置过得DisplayImageOption对象
-  
-         ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(this.getApplicationContext()).defaultDisplayImageOptions(options)
-                 .threadPriority(Thread.NORM_PRIORITY - 2).denyCacheImageMultipleSizesInMemory()
-                 .discCacheFileNameGenerator(new Md5FileNameGenerator()).tasksProcessingOrder(QueueProcessingType.LIFO).build();
-         ImageLoader.getInstance().init(config);
-     }
- }
 
后续:显示图片所使用的uri:
- String imageUri = "http://site.com/image.png"; // from Web
- String imageUri = "file:///mnt/sdcard/image.png"; // from SD card
- String imageUri = "content://media/external/audio/albumart/13"; // from content provider
- String imageUri = "assets://image.png"; // from assets
- String imageUri = "drawable://" + R.drawable.image; // from drawables (only images, non-9patch)
 
注意:使用drawable://除非你真的需要他。时刻要注意使用本地图片加载方法:setImageResource带代替ImageLoader。
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