Android在旋轉時保存值

Question

我是新來的android，並試圖在屏幕旋轉時保存一個布爾值，基本上我的問題是當前：當用戶在主要活動中按下「作弊」按鈕時，他被重定向到一個新的活動，他點擊一個按鈕「顯示答案」，布爾變量mIsCheater設置爲true，但是當屏幕旋轉時，該值變爲false。

下面是代碼：

package com.example.macbookair.androidbooktutorials; 

import android.content.Intent; 
import android.os.PersistableBundle; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.View; 
import android.widget.Button; 
import android.widget.ImageButton; 
import android.widget.TextView; 
import android.widget.Toast; 

import com.example.macbookair.androidbooktutorials.Models.TrueFalse; 

public class MainActivity extends AppCompatActivity { 

    private static final String KEY_INDEX = "index"; 
    private static final String BOOLEAN_INDEX = "index"; 

    private Button mTrueButton,mFalseButton,mCheatButton; 
    private ImageButton mNextButton; 
    private ImageButton mPrevButton; 
    private TextView mQuestionTextView; 
    private int mCurrentIndex = 0; 
    private boolean mIsCheater; 

    private TrueFalse[] mQuestionBank = new TrueFalse[] { 
      new TrueFalse(R.string.question_africa,false), 
      new TrueFalse(R.string.question_oceans,true), 
      new TrueFalse(R.string.question_mideast,false), 
      new TrueFalse(R.string.question_africa,true), 
      new TrueFalse(R.string.question_asia,true) 
    }; 





    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     mCheatButton = (Button) findViewById(R.id.cheat_button); 

     if(savedInstanceState != null) { 
      mCurrentIndex = savedInstanceState.getInt(KEY_INDEX,0); 
      boolean theValue = savedInstanceState.getBoolean(BOOLEAN_INDEX); 
      Log.d("Is that true? -> ", mIsCheater + " "); 
     } 


     mTrueButton = (Button) findViewById(R.id.true_button); 
     mFalseButton = (Button) findViewById(R.id.false_button); 


     mQuestionTextView = (TextView) findViewById(R.id.question_text_view); 



     mNextButton = (ImageButton) findViewById(R.id.button_next); 
     mPrevButton = (ImageButton) findViewById(R.id.button_prev); 

     updateQuestion(); 

     mCheatButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       Intent i = new Intent(MainActivity.this, CheatActivity.class); 
       boolean answerIsTrue = mQuestionBank[mCurrentIndex].isTrueQuestion(); 
       i.putExtra(CheatActivity.EXTRA_ANSWER_IS_TRUE,answerIsTrue); 
//    startActivity(i); 
       startActivityForResult(i,0); 
      } 
     }); 

     mPrevButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       if (mCurrentIndex > 0) { 
        mCurrentIndex = (mCurrentIndex - 1) % mQuestionBank.length; 
        updateQuestion(); 
       } else { 
        Toast.makeText(MainActivity.this,R.string.message,Toast.LENGTH_SHORT).show(); 
       } 
      } 
     }); 

     mQuestionTextView.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       mCurrentIndex = (mCurrentIndex +1) % mQuestionBank.length; 
       updateQuestion(); 
      } 
     }); 

     mNextButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       mCurrentIndex = (mCurrentIndex +1) % mQuestionBank.length; 
       mIsCheater = false; 
       updateQuestion(); 
      } 
     }); 

     mTrueButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       checkedAnswer(true); 
      } 
     }); 

     mFalseButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       checkedAnswer(false); 
      } 
     }); 
    } 

    private void updateQuestion() { 
     int question = mQuestionBank[mCurrentIndex].getmQuestion(); 
     mQuestionTextView.setText(question); 
    } 

    private void checkedAnswer(boolean isTrue) { 
     boolean answer = mQuestionBank[mCurrentIndex].isTrueQuestion(); 

     int messageId = 0; 

     if(mIsCheater) { 
      messageId = R.string.judgment_toast; 
     } 

     if(isTrue == answer) { 
      messageId = R.string.correct_toast; 
     } else { 
      messageId = R.string.incorrect_toast; 
     } 
     Toast.makeText(this,messageId,Toast.LENGTH_SHORT).show(); 
    } 

    @Override 
    public void onSaveInstanceState(Bundle outState) { 
     super.onSaveInstanceState(outState); 
     outState.putInt(KEY_INDEX,mCurrentIndex); 
     outState.putBoolean(BOOLEAN_INDEX, mIsCheater); 
     Log.d("What value is there? ->", mIsCheater + " "); 

    } 

    @Override 
    protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
     super.onActivityResult(requestCode, resultCode, data); 
     if(data == null) { 
      return; 
     } 
     mIsCheater = data.getBooleanExtra(CheatActivity.EXTRA_ANSWER_SHOWN,false); 
    } 
} 

而且從第二個活動，以防萬一代碼：

package com.example.macbookair.androidbooktutorials; 

import android.content.Intent; 
import android.os.PersistableBundle; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.Button; 
import android.widget.TextView; 

public class CheatActivity extends AppCompatActivity { 

    private boolean mAnswerIsTrue; 
    private TextView mAnswerTextView; 
    private Button mShowAnswer; 


    public static final String EXTRA_ANSWER_IS_TRUE = "com.example.macbookair.androidbooktutorials.answer_is_true"; 
    public static final String EXTRA_ANSWER_SHOWN = "com.example.macbookair.androidbooktutorials.answer_is_showed"; 
    public static final String INDEX = "cheatIndex"; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.cheat_activity); 

     mAnswerTextView = (TextView) findViewById(R.id.answerTextView); 
     if(savedInstanceState != null) { 
      String text = savedInstanceState.getString(INDEX,mAnswerTextView.toString()); 
      mAnswerTextView.setText(text); 
     } 

     mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, false); 

     mShowAnswer = (Button) findViewById(R.id.showAnswerButton); 

     setAnswerShownResult(false); 

     mShowAnswer.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       if (mAnswerIsTrue) { 
        mAnswerTextView.setText(R.string.true_button); 
       } else { 
        mAnswerTextView.setText(R.string.false_button); 
       } 
       setAnswerShownResult(true); 
      } 
     }); 



    } 

    @Override 
    protected void onSaveInstanceState(Bundle outState) { 
     super.onSaveInstanceState(outState); 
     outState.putString(INDEX, mAnswerTextView.getText().toString()); 

    } 


    private void setAnswerShownResult(boolean isAnswerShown) { 
     Intent data = new Intent(); 
     data.putExtra(EXTRA_ANSWER_SHOWN, isAnswerShown); 
     setResult(RESULT_OK, data); 
    } 


} 

Answer 1

你有這樣的

mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, false); 

但是當你旋轉，我不除非你明確地自己做，否則不會認爲意圖數據會被保存。

您還需要保存mAnswerIsTrue內onSaveInstanceState和內onCreate或onRestoreInstanceState

而且找回它，如果我沒記錯，你應該之前super.onSaveInstanceState(outState);