Question

在我的应用程序中，我想在后台执行位图转换，因为我面临内存泄漏问题。我知道，可以使用Async Task完成，但不知道如何执行此操作。下面我发布了我的代码。

package com.android.album3;

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;

public class Album3Activity extends Activity 
{
File [] mediaFiles;
File imageDir;
static GridView gridView;
ImageAdapter adapter;
Intent in;
String name = null;
ArrayList<Bitmap> bmpArray = new ArrayList<Bitmap>();
ArrayList<String> fileName = new ArrayList<String>();
public static final String TAG = "Album3Activity";
public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    imageDir = new File(Environment.getExternalStorageDirectory().toString()+
             "/diplomat");
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    if(imageDir.exists())
    {
        setContentView(R.layout.grid);
        mediaFiles = imageDir.listFiles();
        //Log.d("Length of images",""+mediaFiles.length);
        for(File file : mediaFiles)
        {
            bmpArray.add(convertToBitmap(file));
            fileName.add(readFileName(file));
            Log.d(TAG + "bmpArray Size", ""+bmpArray.size());
            Log.d(TAG, "call to convertToBitmap");
        }//for

        adapter = new ImageAdapter(this, bmpArray, fileName);
        gridView = (GridView)findViewById(R.id.gridview);
        gridView.setAdapter(adapter);
        gridView.setOnItemClickListener(new OnItemClickListener() 
        {

        public void onItemClick(AdapterView<?> arg0, View arg1, int position,
                long arg3) 
        {
            in = new Intent(getApplicationContext(), FullScreen.class);
            in.putExtra("id", position);
            startActivity(in);
        }//onItemClick
    });
    }//if
    else
    {
        setContentView(R.layout.no_media);
        //Toast.makeText(Album3Activity.this, "No files available", Toast.LENGTH_SHORT).show();
    }//else
}//onCreate

public static Bitmap convertToBitmap(File file) 
{
    URL url = null;
    try 
    {
        url = file.toURL();
    }//try 
    catch (MalformedURLException e1) 
    {
        Log.d(TAG, e1.toString());
    }//catch

    Bitmap bmp = null;
    try
    {
       bmp = BitmapFactory.decodeStream(url.openStream());
       //bmp.recycle();
    }//try
    catch(Exception e)
    {
        Log.d(TAG, "Exception: "+e.toString());
    }//catch
    return bmp;
}//convertToBitmap

public String readFileName(File file)
{
    String name = file.getName();
    return name;
}//readFileName
}//class

Answer 1

你面临着像记忆问题，因为你的图像尺寸很大，你使用像这样的BitmapFactory解码这个图像

BitmapFactory.Options option = new BitmapFactory.Options();
                option.inSampleSize = 2;//any integer value greater than 1
                Bitmap bm = BitmapFactory.decodeFile(root.getPath() + "/"
                        + imageName,option);
                imageView.setImageBitmap(bm);

如果设置为值＆gt;如图1所示，请求解码器对原始图像进行二次采样，返回较小的图像以节省存储器。样本大小是任一维度中对应于解码位图中的单个像素的像素数。例如，inSampleSize == 4返回的图像是原始宽度/高度的1/4，像素数量的1/16。任何值＆lt; = 1都被视为1.注意：解码器将尝试满足此请求，但生成的位图可能具有与请求完全相同的不同维度。此外，2的幂通常更快/更容易让解码器兑现。

在后台执行位图转换

1 个答案: