Java 保存和读取共享首选项不起作用
尝试通过android培训学习编写android应用程序。我想把东西保存到SharedReferences上 我有一个活动,当你按下一个按钮,运行这个代码Java 保存和读取共享首选项不起作用,java,android,android-sharedpreferences,Java,Android,Android Sharedpreferences,尝试通过android培训学习编写android应用程序。我想把东西保存到SharedReferences上 我有一个活动,当你按下一个按钮,运行这个代码 public void saveMessage(String message){ //Save message local SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE); SharedPreferences.Editor edit
public void saveMessage(String message){
//Save message local
SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString("message",message);
editor.commit();
}
以及显示时运行此代码的另一个活动
public String getMessage(){
SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE);
String message = sharedPref.getString("message","default");
return message;
}
这两种方法应该保存/读取一些数据。我真的不知道我做错了什么
课程的全部代码:
MainActivity.java
package com.example.myfirstapp;
import ...;
public class MainActivity extends AppCompatActivity {
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
/** Called when the User clicks the Send button */
public void sendMessage(View view) {
Intent intent = new Intent(this, DisplayMessageActivity.class);
EditText editText = (EditText) findViewById(R.id.edit_message);
String message = editText.getText().toString();
saveMessage(message);
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);
}
public void saveMessage(String message){
//Save message local
SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString("message",message);
editor.commit();
}
}
package com.example.myfirstapp;
import ...;
public class DisplayMessageActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_display_message);
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
message = getMessage();
TextView textView = new TextView(this);
textView.setTextSize(40);
textView.setText(message);
ViewGroup layout = (ViewGroup) findViewById(R.id.activity_display_message);
layout.addView(textView);
}
public String getMessage(){
SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE);
String message = sharedPref.getString("message","default");
return message;
}
}
DisplayMessageActivity.java
package com.example.myfirstapp;
import ...;
public class MainActivity extends AppCompatActivity {
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
/** Called when the User clicks the Send button */
public void sendMessage(View view) {
Intent intent = new Intent(this, DisplayMessageActivity.class);
EditText editText = (EditText) findViewById(R.id.edit_message);
String message = editText.getText().toString();
saveMessage(message);
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);
}
public void saveMessage(String message){
//Save message local
SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString("message",message);
editor.commit();
}
}
package com.example.myfirstapp;
import ...;
public class DisplayMessageActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_display_message);
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
message = getMessage();
TextView textView = new TextView(this);
textView.setTextSize(40);
textView.setText(message);
ViewGroup layout = (ViewGroup) findViewById(R.id.activity_display_message);
layout.addView(textView);
}
public String getMessage(){
SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE);
String message = sharedPref.getString("message","default");
return message;
}
}
根据安卓的说法:
使用方法管理活动持久状态
getPreferences(int)
,允许您检索和修改一组
与活动关联的名称/值对。要使用
在多个应用程序组件(活动、,
接收方、服务、提供者),您可以使用底层
Context.getSharedReferences()
方法检索首选项对象
以特定的名称存储
因此,如果您想在不同的活动之间共享数据,我认为您可能必须使用getSharedReferences()
方法
要编写的示例代码:
SharedPreferences sharedPref = getSharedPreferences("PREF_NAME", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString("message",message);
editor.commit();
尝试改用
SharedReferences SharedReferences=PreferenceManager.GetDefaultSharedReferences(此选项)代码>