Android-startActivityForResult用法

• 从子Activity获取返回结果
  public void startActivityForResult(Intent intent, int requestCode)
  该方法的第一个参数是intent,第二个参数是请求代码。请求代码先发送给子activity,然后再返回给父activity的用户定义整数值。当一个activity启动多个不同类型的子activity,且需要判断区分消息回馈方时，通常会用到该请求代码

• 设置返回结果
  public final void setResult(int resultCode)
  public final void setResult(int resultCode,Intent data)
  一般来说，参数resultCode可以是以下两个预定义常量中的任何一个
  Activity.RESULT_OK
  Activity.RESULT_CANCELED

• 一个例子的效果图
  

• Demo目录
  

• 字符串资源

    <string name="one">1+1=?string>
    <string name="two">2+2=?string>

    <string name="one_answer">2string>
    <string name="two_answer">4string>

• activity_main.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/btn1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/one"/>

    <Button
        android:id="@+id/btn2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/two"/>
LinearLayout>

• MainActivity.java

public class MainActivity extends AppCompatActivity {

    private static final int REQUEST_ONE = 1;
    private static final int REQUEST_TWO = 2;

    private Button btn1;
    private Button btn2;

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

        btn1 = (Button) findViewById(R.id.btn1);
        btn2 = (Button) findViewById(R.id.btn2);

        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivityForResult(ChooseActivity.newIntent(MainActivity.this), REQUEST_ONE);
            }
        });

        btn2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivityForResult(ChooseActivity.newIntent(MainActivity.this), REQUEST_TWO);
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == RESULT_OK) {
            showResult(requestCode,ChooseActivity.getResultAnswer(data));
        }
    }

    private void showResult(int requestCode, int answer) {
        String str;
        if (requestCode == answer) {
            str = "正确";
        } else {
            str = "错误";
        }
        Snackbar.make(this.getWindow().getDecorView(), str, Snackbar.LENGTH_LONG).setAction("Action", null).show();
    }
}

• activity_choose.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_choose"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/btn1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/one_answer"/>

    <Button
        android:id="@+id/btn2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/two_answer"/>
LinearLayout>

• ChooseActivity.java

public class ChooseActivity extends AppCompatActivity {

    public static final String RESULT_ANSWER = "result_answer";

    public static Intent newIntent(Context context) {
        return new Intent(context, ChooseActivity.class);
    }

    public static int getResultAnswer(Intent intent) {
        return intent.getIntExtra(RESULT_ANSWER, 0);
    }

    private Button btn1;
    private Button btn2;

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

        btn1 = (Button) findViewById(R.id.btn1);
        btn2 = (Button) findViewById(R.id.btn2);

        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent();
                i.putExtra(RESULT_ANSWER, 1);
                setResult(RESULT_OK, i);
                finish();
            }
        });

        btn2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent();
                i.putExtra(RESULT_ANSWER, 2);
                setResult(RESULT_OK, i);
                finish();
            }
        });
    }
}

• 如果要使用Snackbar，要加入依赖

    compile 'com.android.support:design:24.0.0-beta1'