Passing Data Between Activities

Step1: 在接收方的Activity中創建一個newIntent方法【依賴倒置原則，甲方纔知道自己需要什麼數據】

private static final String EXTRA_ANSWER_IS_TRUE =
        "com.bignerdranch.android.geoquiz.answer_is_true";
public static Intent newIntent(Context packageContext, boolean answerIsTrue) {
    Intent intent = new Intent(packageContext, CheatActivity.class);
    intent.putExtra(EXTRA_ANSWER_IS_TRUE, answerIsTrue);
    return intent;
}

Step2: Launching CheatActivity with an extra（在發送方中創建新的activity）

boolean answerIsTrue = mQuestionBank[mCurrentIndex].isAnswerTrue();
Intent intent = CheatActivity.newIntent(QuizActivity.this, answerIsTrue);
startActivity(intent);

Step3: 保存發送方發送的數據

private boolean mAnswerIsTrue;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_cheat);
    mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, false);
}

Step4: 接收方應用發送來的數據

mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, false);
mShowAnswerButton = (Button) findViewById(R.id.show_answer_button);
mShowAnswerButton.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);
        }
    }
});

Getting a result back from a child activity

Step1: 給子activity發送一個請求碼以標識

startActivityForResult(intent, REQUEST_CODE_CHEAT); //給子activity發送一個請求碼

Step2: 把子activity中用戶操作返回給前一個activity

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

Step3: 訪問子activity發送來的數據

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (resultCode != Activity.RESULT_OK) {
        return;
    }
    if (requestCode == REQUEST_CODE_CHEAT) {
        if (data == null) {
            return;
        }
        mIsCheater = CheatActivity.wasAnswerShown(data);
    }
}

Step4: 應用返回的數據

private void checkAnswer(boolean userPressedTrue) {
    boolean answerIsTrue = mQuestionBank[mCurrentIndex].isAnswerTrue();
    int messageResId = 0;
    if (mIsCheater) {
        messageResId = R.string.judgment_toast;
    } else {
        if (userPressedTrue == answerIsTrue) {
            messageResId = R.string.correct_toast;
        } else {
            messageResId = R.string.incorrect_toast;
        }
    }
    Toast.makeText(this, messageResId, Toast.LENGTH_SHORT).show();
}