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Android - External Storage

与内部存储一样，无涯教程能够从设备外部存储器(如SDCard)中浏览或读取数据。 FileInputStream和FileOutputStream类用于读取和写入文件。

读写数据示例

从面板上拖动2个edittexts，2个textviews和2个按钮，现在activity_main.xml文件将如下所示:

File: activity_main.xml

<!--?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.learnfk.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></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"></edittext>
    <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>
    <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:"></textview>
    <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>
    <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"></button>
</relativelayout>

您需要提供write_external_storage权限。

无涯教程网

链接：https://www.learnfk.comhttps://www.learnfk.com/android/android-external-storage-example.html

来源：LearnFk无涯教程网

复制代码

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

File: Activity_Manifest.xml

复制代码

<!--?xml version="1.0" encoding="utf-8"?-->
<manifest
    xmlns:android="http://schemas.android.com/apk/res/android" package="example.learnfk.com.externalstorage">
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
    <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"></action>
                <category android:name="android.intent.category.LAUNCHER"></category>
            </intent-filter>
        </activity>
    </application>
</manifest>

让无涯教程编写代码来编写和读取来自Android外部存储的数据。

File: MainActivity.java

复制代码

package example.learnfk.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=findViewById(R.id.editText2);
        saveButton=findViewById(R.id.button1);
        readButton=findViewById(R.id.button2);

        //对保存按钮执行操作
        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();}
            }
        });

        //对读取按钮执行操作
        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();
            }
        });
    }
}