Android 读取手机SD卡根目录下某个txt文件的文件内容

1.先看activity_main.xml文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:android1="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout
	    android:orientation="horizontal"
	    android:layout_width="fill_parent"
	    android:layout_height="wrap_content" >
	    <TextView  
		    android:textSize="18dip"
		    android:layout_width="wrap_content" 
		    android:layout_height="wrap_content" 
		    android:text="文件名: /sdcard/" />
	    <EditText 
		    android:hint="xname.txt"
		    android:id="@+id/ET_Folder" 
		    android:layout_width="180dip" 
		    android:layout_height="wrap_content" />
	</LinearLayout>
	    
    <LinearLayout
	    android:orientation="horizontal"
	    android:layout_width="fill_parent"
	    android:layout_height="wrap_content" >
	   <Button 
		     android:text="打开" 
		     android:id="@+id/But_Open" 
		     android:layout_width="wrap_content"                                                        
		     android:layout_height="wrap_content" />
	   <Button 
		     android:text="清除" 
		     android:id="@+id/But_Clear" 
		     android:layout_width="wrap_content"                                                        
		     android:layout_height="wrap_content" />
	</LinearLayout>

    <ScrollView 
		android:id="@+id/ScrollView01" 
		android:layout_width="fill_parent" 
		android:layout_height="wrap_content">
		<EditText 
			android:editable="false"
			android:id="@+id/ET_FileContent" 
			android:layout_width="fill_parent" 
			android:layout_height="wrap_content" />
   </ScrollView>
    
</LinearLayout>

2.MainActivity.java文件

/*读取手机SD卡根目录下某个txt文件的文件内容 
 * */

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import android.os.Bundle;
import android.os.Environment;
import android.app.Activity;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
	
	private EditText et_folder;			//输入的文件夹名
	private Button bt_open;				//打开按钮
	private Button bt_clear;			//清除按钮
	private EditText et_filecontent;	//用于显示txt文件内容
	
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		et_folder = (EditText) findViewById(R.id.ET_Folder);
        et_filecontent = (EditText) findViewById(R.id.ET_FileContent);
        
		bt_open = (Button) findViewById(R.id.But_Open); 
		bt_open.setOnClickListener(new OnClickListener(){//打开按钮监听
			public void onClick(View arg0) {
				//若输入的文件夹名为空
				if(et_folder.getText().toString().trim().equals("")){
					Toast.makeText(getApplicationContext(), "输入为空",
							Toast.LENGTH_SHORT).show();
				}else{
					//获得SD卡根目录路径   "/sdcard"
					File sdDir = Environment.getExternalStorageDirectory();
					//根目录下某个txt文件名
					File path = new File(sdDir+File.separator
					 +et_folder.getText().toString().trim());
					
					// 判断SD卡是否存在，并且是否具有读写权限
					if (Environment.getExternalStorageState()
						.equals(Environment.MEDIA_MOUNTED)) {  
			            et_filecontent.setText("");
			            
			            et_filecontent.setText(getFileContent(path));
					}
				}
			}
		});
		
		bt_clear = (Button) findViewById(R.id.But_Clear); 
		bt_clear.setOnClickListener(new OnClickListener(){//清除按钮监听
			public void onClick(View arg0) {
				et_folder.setText("");
	            et_filecontent.setText("");				
			}
		});
		
	}
	
	//读取指定目录下的所有TXT文件的文件内容
	protected String getFileContent(File file) {
		String content  = "";
		if (file.isDirectory() ) {	//检查此路径名的文件是否是一个目录(文件夹)
            Log.i("zeng", "The File doesn't not exist "
            	+file.getName().toString()+file.getPath().toString());   
        } else {
            if (file.getName().endsWith(".txt")) {//文件格式为txt文件
            	try {
                    InputStream instream = new FileInputStream(file); 
                    if (instream != null) {
                        InputStreamReader inputreader
                        	=new InputStreamReader(instream, "GBK");
                        BufferedReader buffreader = new BufferedReader(inputreader);
                        String line="";
                        //分行读取
                       while (( line = buffreader.readLine()) != null) {
                            content += line + "\n";
                        }                
                        instream.close();		//关闭输入流
                    }
                }
                catch (java.io.FileNotFoundException e) {
                    Log.d("TestFile", "The File doesn't not exist.");
                } 
                catch (IOException e)  {
                     Log.d("TestFile", e.getMessage());
                }
            }
		}
		return content ;
	}
}