2.SD卡读写操作
1读写sd卡首先得添加读写权限
2.建一个布局文件,用来接收和展示数据
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
<Button
android:id="@+id/buttonWrite"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="写入数据"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<EditText
android:id="@+id/edit"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/buttonWrite"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
<Button
android:id="@+id/buttonReade"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="读取数据"
android:layout_below="@+id/edit"
android:layout_alignLeft="@+id/buttonWrite"
android:layout_alignStart="@+id/buttonWrite"
android:layout_marginTop="73dp" />
<TextView
android:id="@+id/textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="yu"
android:textSize="20sp"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="167dp" />
</RelativeLayout>
package xiaocool.net.sdtest;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
public class MainActivity extends ActionBarActivity {
private final String FILE_NAME="/xiaocool.bin";
private Button write,read;
private EditText editText;
private TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
write=(Button)this.findViewById(R.id.buttonWrite);
read=(Button)this.findViewById(R.id.buttonReade);
editText=(EditText)this.findViewById(R.id.edit);
textView=(TextView)this.findViewById(R.id.textview);
write.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Write(editText.getText().toString());
editText.setText("");
}
});
read.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
textView.setText(Read());
}
});
}
//往sd卡写入数据的方法
private void Write(String content){
try{
//如果手机插入了sd卡,而且 具有访问sd卡的权限
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
//获取sd卡的目录
File sdCradDir=Environment.getExternalStorageDirectory();
File targetFile=new File(sdCradDir.getCanonicalPath()+FILE_NAME);
//以指定文件创建RandomAccessFile
RandomAccessFile raf=new RandomAccessFile(targetFile,"rw");
//将文件记录指针移到最后
raf.seek(targetFile.length());
//输出文件内容
raf.write(content.getBytes());
//关闭
raf.close();
}
}catch (Exception E){
E.printStackTrace();
}
}
//从sd卡读取数据
private String Read(){
try {
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
File sdCardDir=Environment.getExternalStorageDirectory();
//获取制定文件对应的输入流
FileInputStream file=new FileInputStream(sdCardDir.getCanonicalPath()+FILE_NAME);
//将制定的输入流包装成BufferReader
BufferedReader br=new BufferedReader(new InputStreamReader(file));
StringBuilder sb=new StringBuilder("");
String line=null;
//循环读取文件内容
while((line=br.readLine())!=null){
sb.append(line);
}
//关闭
br.close();
return sb.toString();
}
}catch (Exception E){
E.printStackTrace();
}
return null;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
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