（1）程序说明

1）首先要添加文件创建，删除，和写入数据的权限

2）接着扩展fileobseerver，写SDk文件监听类。可以查看下文的文件监听器源码

3）如何启动文件监控？

对于Activity来说通常在onResume（）方法中调用startwatching（）来启动文件监控。

在onPause（）方法中调用stopwatching（）来取消文件监控。

（2）布局文件

（3）文件监听器源码：

1）扩展的Fileobserver，实现文件或者文件夹的监听

package com.liuzuyi.fileobserver;
import android.os.FileObserver;
import android.util.Log;
public class SDCardListener extends FileObserver {
public SDCardListener(String path) {
super(path);
}
public void onEvent(int event, String path) {
switch (event) {
case FileObserver.CREATE : Log.d("creat", "filename"+path);
break;
case FileObserver.ALL_EVENTS : Log.d("all", "filename"+path);
break;
}
}
}

2）主程序代码

package com.liuzuyi.fileobserver;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
private EditText filename;
private EditText content;
private TextView textcontent;
private static final String TAG ="simplefile";
SDCardListener myfileListener = new SDCardListener("/sdcard");
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
filename =(EditText)findViewById(R.id.filename);
content =(EditText)findViewById(R.id.content);
textcontent =(TextView)findViewById(R.id.textcontent);
Button savebutton =(Button)this.findViewById(R.id.savebutton);
Button viewbutton =(Button)this.findViewById(R.id.readbutton);
savebutton.setOnClickListener(listener);
viewbutton.setOnClickListener(listener);
}
public void onResume() {
super.onResume();
myfileListener.startWatching();
}
public void onPause() {
super.onPause();
myfileListener.stopWatching();
}
private View.OnClickListener listener = new OnClickListener() {
public void onClick(View v) {
Button button =(Button)v;
String namestr =filename.getText().toString().trim();
String contentStr =content.getText().toString();
switch ( button.getId() ) {
case R.id.savebutton: String res ="success";
try {
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
FileOutputStream outstream = new FileOutputStream("/sdcard/"+namestr+".txt");
outstream.write(contentStr.getBytes() );
outstream.close();
}
else return ;
}
catch (Exception e) {
res= "failure";
e.printStackTrace();
}
Toast.makeText(MainActivity.this, res ,Toast.LENGTH_LONG).show();
Log.i(TAG, namestr);
Log.i(TAG, contentStr);
break;
case R.id.readbutton: String resid_v ="success";
String contentst = null;
try {
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
File SDCardDir=Environment.getExternalStorageDirectory();
File saveFile = new File(SDCardDir,namestr+".txt");
FileInputStream instream = new FileInputStream(saveFile);
ByteArrayOutputStream Ostream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = -1;
while( (len = instream.read(buffer)) != -1 ) {
Ostream.write(buffer,0,len);
}
contentst = Ostream.toString();
Ostream.close();
instream.close();
}
else {
Toast.makeText(MainActivity.this, "SD卡不存在", Toast.LENGTH_LONG).show();
}
}
catch (Exception e) {
resid_v ="faile";
e.printStackTrace();
}
textcontent.setText( contentst);
Log.i(TAG, contentst);
Toast.makeText(MainActivity.this, resid_v,Toast.LENGTH_LONG).show();
Log.i(TAG,namestr);
break;
}
}
}
;
}