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

• activity_main.xml

<?xml version="1.0" encoding="utf-8"?><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

<?xml version="1.0" encoding="utf-8"?><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'