（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
<?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" >
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:id="@+id/label_01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/name"
android:textSize="20dp" />
<EditText
android:id="@+id/filename"
android:layout_width="160dp"
android:layout_height="wrap_content"
android:layout_alignTop="@id/label_01"
android:layout_toRightOf="@id/label_01" />
</RelativeLayout>
<TextView
android:id="@+id/label_02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/neirong" />
<EditText
android:id="@+id/content"
android:layout_width="fill_parent"
android:layout_height="120px"
android:ems="10" >
<requestFocus />
</EditText>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<Button
android:id="@+id/savebutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="right"
android:text="@string/save" />
<Button
android:id="@+id/readbutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="right"
android:text="@string/read" />
</LinearLayout>
<TextView
android:id="@+id/textcontent"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="0.10" />
</LinearLayout>
（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;
}
}
};
}