android-查看关键字是否存在的文件

package zhang.example;

import java.io.File;

import android.app.Activity;
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 search extends Activity {
private Button ok;
private TextView tv;
private EditText et;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

ok=(Button)findViewById(R.id.button1);
tv=(TextView)findViewById(R.id.textView1);
et=(EditText)findViewById(R.id.editText1);

ok.setOnClickListener(new Button.OnClickListener(){

@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
String key=et.getText().toString();
if(key.equalsIgnoreCase("")){
Toast.makeText(search.this, "xxx", Toast.LENGTH_SHORT).show();
}
else{
tv.setText(searchFile(key));
}
}});

}
private String  searchFile(String key){
String result="";
File[] files=new File("/").listFiles();
for(File f:files){
if(f.getName().indexOf(key)>=0){
result+=f.getPath()+"\n";
}
}
if(result.equals(""))
result="no";
return result;

}
}

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

android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="key word"
/>
<EditText android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/editText1"></EditText>
<Button android:text="Button" android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
<TextView  android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content"></TextView>
</LinearLayout>