android外部存储示例 android外部存储|Android

像内部存储一样，我们能够从设备外部存储器（例如sdcard）中保存或读取数据。 FileInputStream和FileOutputStream类用于读取和写入数据到文件中。
在android外部存储中读写数据的示例
activity_main.xml从面板上拖出2个edittext，2个textviews和2个按钮，现在activity_main.xml文件将如下所示：

< ?xml version="1.0" encoding="utf-8"?> < RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="example.srcmini.com.externalstorage.MainActivity">< EditText android:id="@+id/editText1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentRight="true" android:layout_alignParentTop="true" android:layout_marginRight="20dp" android:layout_marginTop="24dp" android:ems="10" >< requestFocus /> < /EditText>< EditText android:id="@+id/editText2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignRight="@+id/editText1" android:layout_below="@+id/editText1" android:layout_marginTop="24dp" android:ems="10" />< TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/editText1" android:layout_alignBottom="@+id/editText1" android:layout_alignParentLeft="true" android:text="File Name:" />< TextView android:id="@+id/textView2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/editText2" android:layout_alignBottom="@+id/editText2" android:layout_alignParentLeft="true" android:text="Data:" />< Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/editText2" android:layout_below="@+id/editText2" android:layout_marginLeft="70dp" android:layout_marginTop="16dp" android:text="save" />< Button android:id="@+id/button2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/button1" android:layout_alignBottom="@+id/button1" android:layout_toRightOf="@+id/button1" android:text="read" /> < /RelativeLayout>

提供外部存储的权限你需要提供WRITE_EXTERNAL_STORAGE权限。

< uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

< ?xml version="1.0" encoding="utf-8"?> < manifest xmlns:android="http://schemas.android.com/apk/res/android" package="example.srcmini.com.externalstorage"> < uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> < application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"> < activity android:name=".MainActivity"> < intent-filter> < action android:name="android.intent.action.MAIN" />< category android:name="android.intent.category.LAUNCHER" /> < /intent-filter> < /activity> < /application>< /manifest>

活动类【android外部存储示例】让我们编写代码以从android外部存储中写入和读取数据。

package example.srcmini.com.externalstorage; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.Toast; import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStreamReader; import java.io.OutputStreamWriter; public class MainActivity extends AppCompatActivity { EditText editTextFileName, editTextData; Button saveButton, readButton; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); editTextFileName=findViewById(R.id.editText1); editTextData=http://www.srcmini.com/findViewById(R.id.editText2); saveButton=findViewById(R.id.button1); readButton=findViewById(R.id.button2); //Performing action on save button saveButton.setOnClickListener(new View.OnClickListener(){@Override public void onClick(View arg0) { String filename=editTextFileName.getText().toString(); String data=editTextData.getText().toString(); FileOutputStream fos; try { File myFile = new File("/sdcard/"+filename); myFile.createNewFile(); FileOutputStream fOut = new FileOutputStream(myFile); OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut); myOutWriter.append(data); myOutWriter.close(); fOut.close(); Toast.makeText(getApplicationContext(), filename + "saved", Toast.LENGTH_LONG).show(); } catch (FileNotFoundException e) {e.printStackTrace(); } catch (IOException e) {e.printStackTrace(); } } }); //Performing action on Read Button readButton.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View arg0) { String filename=editTextFileName.getText().toString(); StringBuffer stringBuffer = new StringBuffer(); String aDataRow = ""; String aBuffer = ""; try { File myFile = new File("/sdcard/"+filename); FileInputStream fIn = new FileInputStream(myFile); BufferedReader myReader = new BufferedReader( new InputStreamReader(fIn)); while ((aDataRow = myReader.readLine()) != null) { aBuffer += aDataRow + "\n"; } myReader.close(); } catch (IOException e) { e.printStackTrace(); } Toast.makeText(getApplicationContext(), aBuffer, Toast.LENGTH_LONG).show(); } }); } }