AsyncTask的用法 ：实现扫描SD卡指定后缀类型的文件

AsyncTask的用法:http://www.cnblogs.com/dawei/archive/2011/04/18/2019903.html

初探异步AsyncTask扫描SD卡:http://www.eoeandroid.com/thread-113400-1-1.html

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

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="输入文件类型"
         >

        <requestFocus />
    </EditText>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="开始扫描" />



    <TextView
        android:id="@+id/textView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="TextView" />

</LinearLayout>

package com.pandy.task;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class AsyncTaskDemoActivity extends Activity {
    /** Called when the activity is first created. */
	private Button button1;
	private EditText editText1;
	private List<String> list;
	private TextView textView1;
	
	
	
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        this.setTitle("Pandy:扫描SD卡的文件类型.");
        
        button1 = (Button)findViewById(R.id.button1);
        editText1 = (EditText)findViewById(R.id.editText1);
        textView1 = (TextView)findViewById(R.id.textView1);
        
        button1.setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				if(editText1.getText()==null||editText1.getText().toString().trim().length()==0){
					Toast.makeText(AsyncTaskDemoActivity.this, "请输入文件类型...",Toast.LENGTH_SHORT).show();
					return;
				}
				
				list = new ArrayList<String>();
				new AsyncTask<Integer,Integer,Integer>(){
					
					private ProgressDialog dialog;

					
					@Override
					protected void onCancelled() {
						// TODO Auto-generated method stub
						super.onCancelled();
					}

					//执行完成之后
					@Override
					protected void onPostExecute(Integer result) {
						// TODO Auto-generated method stub
						dialog.dismiss();
						super.onPostExecute(result);
						Toast.makeText(AsyncTaskDemoActivity.this, "执行完成...",Toast.LENGTH_SHORT).show();
						textView1.setText("");
						if(list!=null){
							for(int i=0; i<list.size(); i++){
								textView1.setText(textView1.getText()+list.get(i)+"\n");
							}
						}
						
					}

					//执行之前
					@Override
					protected void onPreExecute() {
						// TODO Auto-generated method stub
						dialog = ProgressDialog.show(AsyncTaskDemoActivity.this, "Title", "Load......");
						super.onPreExecute();
					}

					//修改界面
					@Override
					protected void onProgressUpdate(Integer... values) {
						// TODO Auto-generated method stub
						super.onProgressUpdate(values);
					}

					//这里开始启动进程
					@Override
					protected Integer doInBackground(Integer... params) {
						// TODO Auto-generated method stub
						//textView1.setText(""); //为什么放在这里就会出错????
						String txt = editText1.getText()==null?"":editText1.getText().toString();
						if(txt.length()<=0) {
							Toast.makeText(AsyncTaskDemoActivity.this, "没有输入文件类型", Toast.LENGTH_LONG);
							return null;
						}
						
						
						String status = android.os.Environment.getExternalStorageState();
						if(android.os.Environment.MEDIA_MOUNTED.equalsIgnoreCase(status)){
							File file = android.os.Environment.getExternalStorageDirectory();
							scanSDCard(file,txt);
							return null;
						}else{
							Toast.makeText(AsyncTaskDemoActivity.this, "不能访问SD卡.", Toast.LENGTH_LONG);
							return null;
						}
						
					}
					
				}.execute(0);
				
			}
		});
        
        
    }
    
    public void scanSDCard(File file,String ext){
    	if(file.isDirectory()){
    		File[] files = file.listFiles();
    		if(files!=null){
    			for(int i=0; i<files.length; i++){
    				File tmp = files[i];
    				if(tmp.isFile()){
    					String fileName = tmp.getName();
        				if(fileName.indexOf(".")>=0){
        					fileName = fileName.substring(fileName.lastIndexOf(".")+1);
        					if(ext!=null&&ext.equalsIgnoreCase(fileName))
        						list.add(tmp.getAbsolutePath());
        				}
    				}else
    					scanSDCard(tmp,ext);
    			}
    		}
    	}else{
    		if(file.isFile()){
				String fileName = file.getName();
				if(fileName.indexOf(".")>=0){
					fileName = fileName.substring(fileName.lastIndexOf(".")+1);
					if(ext!=null&&ext.equalsIgnoreCase(fileName))
						list.add(file.getAbsolutePath());
				}
			}
    	}
    }
}