Android模仿QQ空间图片上传——原理

package com.example.imagedemotext;

import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.content.ContentResolver;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore.Images.Thumbnails;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.GridView;
import android.widget.ImageView;

public class MainActivity extends Activity {
    Button btn_start;
    GridView gridview;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn_start = (Button) findViewById(R.id.btn_start);
        gridview = (GridView) findViewById(R.id.gridview);
        adapter = new Myadapter();
        iniLisner();
        inidata();
    }
    private void refreshAdapter(){
        if(list == null){
            list = new ArrayList<String>();
        }
        if(adapter == null){
            adapter = new Myadapter();
        }
        if(list.size() == ON){
            list.remove(list.size() - 1);
        }
        adapter.notifyDataSetChanged();
    }
    private final int ON = 5;  //允许的图片数量 + 1
    private void inidata() {
        if(list == null){
            list = new ArrayList<String>();
            list.add("a");  //添加默认图片  
        }
        gridview.setAdapter(adapter);
        gridview.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                if(list.get(position).equals("a")){
                    setClick();
                }
            }
        });
        
        refreshAdapter();
    }
    
    Myadapter adapter;
    class Myadapter extends BaseAdapter{
        @Override
        public int getCount() {return list.size();}
        @Override
        public Object getItem(int position) {return null;}
        @Override
        public long getItemId(int position) {return 0;}
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder vh = null;
            if(convertView == null){
                convertView = View.inflate(getApplicationContext(), R.layout.item, null);
                vh = new ViewHolder();
                vh.iamge = (ImageView) convertView.findViewById(R.id.image);
                convertView.setTag(vh);
            }else {
                vh = (ViewHolder) convertView.getTag();
            }
            if(list.get(position).equals("a")){  //添加默认图片  
                vh.iamge.setImageResource(R.drawable.ic_launcher);
            }else {
                Bitmap loacalBitmap = getLoacalBitmap(list.get(position));
                if(loacalBitmap != null){
                    vh.iamge.setImageBitmap(loacalBitmap);
                }
            }
            return convertView;
        }
        
    }
    class ViewHolder {
        ImageView iamge;
    }
    
    private void iniLisner() {
        if(btn_start != null){
            btn_start.setOnClickListener(new OnClickListener() {
                
                @Override
                public void onClick(View v) {
                    setClick();
                }
            });
            
        }
        
    }
    
    private void setClick(){
        Intent getImage = new Intent(Intent.ACTION_GET_CONTENT);
        getImage.addCategory(Intent.CATEGORY_OPENABLE);
        getImage.setType("image/jpeg");
        startActivityForResult(getImage, 0);
        
    }
    private byte[] mContent;
    private List<String> list;
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        ContentResolver resolver = getContentResolver();
        if(data == null){
            return;
        }
        if (requestCode == 0) {
            try {
                Uri originalUri = data.getData();
                mContent = readStream(resolver.openInputStream(Uri.parse(originalUri.toString())));
                String path = originalUri.toString();
                ContentResolver testcr = getContentResolver();
                Cursor cur = testcr.query(originalUri, null, null, null, null);
                if(list.size() == ON){
                    removeItem();
                    refreshAdapter();
                    return;
                }
                removeItem();
                for (cur.moveToFirst(); !cur.isAfterLast(); cur.moveToNext()) {
                    int dataColumn = cur.getColumnIndex(Thumbnails.DATA);
                    String image_path = cur.getString(dataColumn);
                    list.add(image_path);
                }
                list.add("a");
                refreshAdapter();
                
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }

        } 
        
        
    }
    private void removeItem() {
        if(list.size() -1 != ON){
            if(list.size() != 0){  //删除默认图片
                list.remove(list.size() - 1);
            }
        }
        
    }
    public static byte[] readStream(InputStream inStream) throws Exception {
        byte[] buffer = new byte[1024];
        int len = -1;
        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
        while ((len = inStream.read(buffer)) != -1) {
            outStream.write(buffer, 0, len);
        }
        byte[] data = outStream.toByteArray();
        outStream.close();
        inStream.close();
        return data;

    }
    public static Bitmap getLoacalBitmap(String url) {
         try {
              FileInputStream fis = new FileInputStream(url);
              return BitmapFactory.decodeStream(fis);
         } catch (FileNotFoundException e) {
              e.printStackTrace();
              return null;
         }
    }

}

<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="点击按钮选择一个图片后会显示在下面的GridView" />

    <Button
        android:id="@+id/btn_start"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="获取图片" />

    <View
        android:layout_width="match_parent"
        android:layout_height="9dp"
        android:background="#a0000000" />

    <GridView
        android:id="@+id/gridview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </GridView>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/image"
        android:layout_width="40dp"
        android:layout_height="40dp"
 />

</LinearLayout>