java - 从 asynctask 检索共享首选项值

Question

我试图从共享首选项中获取值，但它返回 null。共享首选项值是从 asynctask 设置的。我从 asynctask 内部测试了它，在 toast 中打印 stord 值并且它有效，但问题是当我尝试通过单击按钮注册来检索 asynctask 外部的值时，它显示 null。 logcat 中没有显示错误。

Activity 代码:

package com.example.mohalogin;

import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Properties;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class RegisterActivity extends Activity {
	
	private EditText editTextName;
    private EditText editTextUsername;
    private EditText editTextPassword;
    private EditText editTextEmail;

    private Button buttonRegister;
    private Button buttonLogin;
    //private Button gmail,yahoo;
    Context context;
    
    private SharedPreferences sharedpreferences;
	public static final String MyPREFERENCES = "MyPreferences" ;
	public static final String RegisResult = "result";
    
    
    private static final String REGISTER_URL = "xxxxxxxxxx"; //fake data

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_register);
		
		editTextName = (EditText) findViewById(R.id.editTextName);
        editTextUsername = (EditText) findViewById(R.id.editTextUserName);
        editTextPassword = (EditText) findViewById(R.id.editTextPassword);
        editTextEmail = (EditText) findViewById(R.id.editTextEmail);

        buttonRegister = (Button) findViewById(R.id.buttonRegister);
        buttonLogin = (Button) findViewById(R.id.buttonLogin);
      
       
        buttonRegister.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View arg0){
            	registerUser();
            	
            	sharedpreferences=getApplicationContext().getSharedPreferences("MyPrefs", getApplicationContext().MODE_PRIVATE);
            	
            	buttonLogin.setText(sharedpreferences.getString("result","")); //testing by printing the value in the button
            	
            }
        });
        

        /*buttonLogin.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View arg0){
            	
            	startActivity(new Intent(RegisterActivity.this, LoginActivity.class));
                
            }
        });*/
	}
	
        private void registerUser() {
		
		String name = editTextName.getText().toString().trim().toLowerCase();
        String username = editTextUsername.getText().toString().trim().toLowerCase();
        String password = editTextPassword.getText().toString().trim().toLowerCase();
        String email = editTextEmail.getText().toString().trim().toLowerCase();

        register(name,username,password,email);	
	}
	
	private void register(String name, String username, String password, String email) {
        class RegisterUser extends AsyncTask<String, Void, String> {
        	
        	ProgressDialog loading;
            RegisterUserClass ruc = new RegisterUserClass();
            private Context context2;
            
            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                loading = ProgressDialog.show(RegisterActivity.this, "Please Wait","Registering new user", true, false);
            }

			@Override
			protected String doInBackground(String... params) {
				
				HashMap<String, String> data = new HashMap<String,String>();
                data.put("name",params[0]);
                data.put("username",params[1]);
                data.put("password",params[2]);
                data.put("email",params[3]);

                String result = ruc.sendPostRequest(REGISTER_URL,data);
				
                return  result;
				
			}
			
			@Override
            protected void onPostExecute(String s) {
                super.onPostExecute(s);
                loading.dismiss();
                
                sharedpreferences = context2.getSharedPreferences(MyPREFERENCES, context2.MODE_PRIVATE);
                SharedPreferences.Editor editor = sharedpreferences.edit();
                editor.putString(RegisResult, s);
				editor.commit();

                Toast.makeText(getApplicationContext(),sharedpreferences.getString("result",""), Toast.LENGTH_LONG).show();
                
            }	
			
			public RegisterUser(Context context2)
			{
				this.context2=context2;
			}
        }

        RegisterUser ru = new RegisterUser(getApplicationContext());
        ru.execute(name, username, password, email);

}
}

Answer 1

您的问题在于调用 getSharedPreferences(String, int) -

您基本上使用两个单独的 SharePreference 实例，因为您每次都为 SharedPreferences 传递不同的名称(字符串) -

当您存储该值时，您正在使用getSharedPreferences("MyPreferences", context2.MODE_PRIVATE);

当您尝试获取该值时，您正在使用getSharedPreferences("MyPrefs", getApplicationContext().MODE_PRIVATE);

修改您的代码以使用相同的 SharedPreference 名称，它应该可以工作。