从asynctask中检索共享首选项值

时间：2016-02-15 19:39:46

标签： java android android-asynctask

我正在尝试从共享首选项中获取值，并且它返回null。共享首选项值是从asynctask设置的。我在asynctask中测试它，在toast中打印stord值并且它工作正常，但问题是当我尝试通过单击buttonRegister在asynctask外部检索值时，它显示为null。 logcat中没有显示错误。

活动代码：

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＆＃13; 
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);

}
}
＆＃13;
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5 个答案:

答案 0 :(得分：1)

当您指定要由AsyncTask执行的部分代码时，它实际上是在除Ui线程之外的新线程中执行的。实际上在 ButtonRegister 的 onClick ， registerUser（）和以下两行，在并行模式不是顺序。

如果要确保成功完成SharedPreferences中的保存，可以再次阅读并设置按钮文本。以这种方式更改AsyncTask的 OnPostExecute ：

@Override
protected void onPostExecute(String s) 
{
     super.onPostExecute(s);
     loading.dismiss();
     .
     .
     .


    buttonLogin.setText(sharedpreferences.getString("result",""));
 }

答案 1 :(得分：1)

你的问题是调用getSharedPreferences（String，int） -

您基本上使用两个单独的SharePreference实例，因为每次都为SharedPreferences传递一个不同的名称（String） -

存储值时，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，它应该有效。

答案 2 :(得分：0)

您正在错误的位置访问该值。 请尝试使用此代码:) 

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);
            sharedpreferences=getApplicationContext().getSharedPreferences("MyPrefs", getApplicationContext().MODE_PRIVATE);
            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();





                }
            });


            /*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();
                    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();
                    buttonLogin.setText(sharedpreferences.getString(RegisResult,"")); //testing by printing the value in the button
                }   

                public RegisterUser(Context context2)
                {
                    this.context2=context2;
                }
            }

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

    }
    }

答案 3 :(得分：0)

当您尝试检索asynctask之外的值时，它显示为null，因为asynctask没有完成。无论您在执行asyncTask时获得的数据需要做什么，都需要在onPostExecute内完成，这是您可以确定asyncTask的唯一地方已经完成了。

答案 4 :(得分：0)

提交后重新实例化您的共享偏好。

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