Activity之间传递数据 Intent extra （p86-88）

1.在目的Activity添加extra常量

public class CheatActivity extends AppCompatActivity {
private static final String EXTRA_ANSWER_IS_TRUE =
"com.bignerdranch.android.geoquiz.answer_is_true";

... 

2.目的Activity CheatActivity中的newIntent(...)方法 

public class CheatActivity extends AppCompatActivity {
private static final String EXTRA_ANSWER_IS_TRUE =
"com.bignerdranch.android.geoquiz.answer_is_true";

public static Intent newIntent(Context packageContext, boolean answerIsTrue) {
Intent i = new Intent(packageContext, CheatActivity.class);
i.putExtra(EXTRA_ANSWER_IS_TRUE, answerIsTrue);
return i;
}
...

3.源Activity用一个extra启动

mCheatButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// Start CheatActivity
Intent i = new Intent(QuizActivity.this, CheatActivity.class);
boolean answerIsTrue = mQuestionBank[mCurrentIndex].isAnswerTrue();
Intent i = CheatActivity.newIntent(QuizActivity.this, answerIsTrue);
startActivity(i);
}
}); 

4.目的Activity获取extras信息

public class CheatActivity extends AppCompatActivity {
private static final String EXTRA_ANSWER_IS_TRUE =
"com.bignerdranch.android.geoquiz.answer_is_true";
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);
}
...
} 

使用可返回值方式

1.源Activity加键值调用startActivityForResult(...)方法

public class QuizActivity extends AppCompatActivity {
private static final int REQUEST_CODE_CHEAT = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
...
mCheatButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
boolean answerIsTrue = mQuestionBank[mCurrentIndex].isAnswerTrue();
Intent i = CheatActivity.newIntent(QuizActivity.this, answerIsTrue);
startActivity(i);
startActivityForResult(i, REQUEST_CODE_CHEAT);
}
});
...
2.目的Activity返还intent ，调用Activity.setResult(int, Intent)方法将信息回传给QuizActivity
public class CheatActivity extends AppCompatActivity {
private static final String EXTRA_ANSWER_IS_TRUE =
"com.bignerdranch.android.geoquiz.answer_is_true";
private static final String EXTRA_ANSWER_SHOWN =
"com.bignerdranch.android.geoquiz.answer_shown";
...
@Override
protected void onCreate(Bundle savedInstanceState) {
...
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);//输入值
}
});
}

//用方法包装发送Intent和setResult方法
private void setAnswerShownResult(boolean isAnswerShown) {
Intent data = new Intent();
data.putExtra(EXTRA_ANSWER_SHOWN, isAnswerShown);
setResult(RESULT_OK, data);
}

3.最后覆盖QuizActivity的onActivityResult(int, int, Intent)方法来处理返回结果，需要另一个方法在目的activity协助解析出
QuizActivity能用的信息
public static Intent newIntent(Context packageContext, boolean answerIsTrue) {
Intent i = new Intent(packageContext, CheatActivity.class);
i.putExtra(EXTRA_ANSWER_IS_TRUE, answerIsTrue);
return i;
}
public static boolean wasAnswerShown(Intent result) {
return result.getBooleanExtra(EXTRA_ANSWER_SHOWN, false);
} 

4.源activity QuizActivity处理结果

public class QuizActivity extends AppCompatActivity {
...
private int mCurrentIndex = 0;
private boolean mIsCheater;
...
@Override
protected void onCreate(Bundle savedInstanceState) {
...
}
@Override
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);
}
}
...
}