android 6.3.1 6.3.2
这次与以往不同我在原来的项目上新建个activity，把activity_main.xml修改为<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<EditText
android:id="@+id/edit"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Type something here"
/>
<Button
android:onClick="click"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="start second activity"/>
</LinearLayout>
把mainactivity.java修改为package com.example.xinwei.filepersistencetest;
import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.BufferedWriter;
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 {
private EditText edit;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
edit=(EditText)findViewById(R.id.edit);
String inputText=load();
if(TextUtils.isEmpty(edit.getText())){
edit.setText(inputText);
edit.setSelection(inputText.length());
Toast.makeText(this, "Restoring succeeded", Toast.LENGTH_SHORT).show();
}
}
@Override
protected void onDestroy() {
super.onDestroy();
String inputText=edit.getText().toString();
save(inputText);
}
private void save(String inputText) {
FileOutputStream out=null;
BufferedWriter writer=null;
try {
out=openFileOutput("data", Context.MODE_PRIVATE);
writer=new BufferedWriter(new OutputStreamWriter(out));
writer.write(inputText);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
if(writer!=null){
try {
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public String load(){
FileInputStream in = null;
BufferedReader reader= null;
StringBuilder content = new StringBuilder();
try {
in = openFileInput("data");
reader = new BufferedReader(new InputStreamReader(in));
String line="";
while((line=reader.readLine())!=null){
content.append(line);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
if(reader!=null){
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return content.toString();
}
public void click(View v){
Intent intent = new Intent(this,SecondActivity.class);
startActivity(intent);
}
}
mainactivity.java旁新建SecondActiviy.java空活动，修改activity_second.xml文件<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<Button
android:id="@+id/save_data"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="save data"/>
<Button
android:id="@+id/restore_data"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="restore data"/>
</LinearLayout>
修改SecondActiviy.java文件package com.example.xinwei.filepersistencetest;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class SecondActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
Button button=(Button)findViewById(R.id.save_data);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
SharedPreferences.Editor editor=getSharedPreferences("data1",MODE_PRIVATE).edit();
editor.putString("name","Tom");
editor.putInt("age",28);
editor.putBoolean("married",false);
editor.apply();
}
});
restoreData();
}
private void restoreData() {
Button restoreData = (Button)findViewById(R.id.restore_data);
restoreData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
SharedPreferences pref=getSharedPreferences("data1",MODE_PRIVATE);
String name =pref.getString("name","");
int age = pref.getInt("age",0);
boolean married=pref.getBoolean("married",false);
Toast.makeText(SecondActivity.this, name+age+married, Toast.LENGTH_SHORT).show();
}
});
}
}
在这个文件里有存储和读取数据的逻辑，都非常简单，效果图为：
页:
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