如何在Android中管理startActivityForResult？

本例演示了如何在Android中管理startActivityForResult

步骤1 − 在Android Studio中创建一个新项目，转到文件 ⇒ 新建项目，并填写所有必需的详细信息以创建新项目。

步骤2 − 将以下代码添加到res/layout/activity_main.xml。

<?xml version = "1.0" encoding = "utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
   xmlns:app = "http://schemas.android.com/apk/res-auto"
   xmlns:tools = "http://schemas.android.com/tools"
   android:layout_width = "match_parent"
   android:gravity = "center"
   android:layout_height = "match_parent"
   tools:context = ".MainActivity"
   android:orientation = "vertical">
   <TextView
      android:id = "@+id/actionEvent"
      android:textSize = "40sp"
      android:layout_marginTop = "30dp"
      android:layout_width = "wrap_content"
      android:layout_height = "match_parent" />
</LinearLayout>

在上面的代码中，我们使用TextView来显示Activity结果数据。

步骤3 − 将以下代码添加到src/MainActivity.java

<?xml version = "1.0" encoding = "utf-8"?>
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
   TextView actionEvent;
   @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      actionEvent = findViewById(R.id.actionEvent);
      actionEvent.setText("Click");
      actionEvent.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            Intent i = new Intent(MainActivity.this, SecondActivity.class);
            startActivityForResult(i, 1);
         }
      });
   }
   @Override
   protected void onActivityResult(int requestCode, int resultCode, Intent data) {
      super.onActivityResult(requestCode, resultCode, data);
      if (requestCode == 1) {
         if (resultCode == RESULT_OK) {
            String returnString = data.getStringExtra("result");
            actionEvent.setText(returnString);
         }
      }
   }
}

步骤3 − 将以下代码添加到src/SecondActivity.java

<?xml version = "1.0" encoding = "utf-8"?>
import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class SecondActivity extends AppCompatActivity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_second);
      Intent returnIntent = new Intent();
      returnIntent.putExtra("result","data from seconActivity");
      setResult(Activity.RESULT_OK,returnIntent);
      finish();
   }
}

步骤3 − 将以下代码添加到activity_second.xml

<?xml version = "1.0" encoding = "utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android = "http://schemas.android.com/apk/res/android"
   xmlns:app = "http://schemas.android.com/apk/res-auto"
   xmlns:tools = "http://schemas.android.com/tools"
   android:layout_width = "match_parent"
   android:layout_height = "match_parent"
   tools:context = ".SecondActivity">
</android.support.constraint.ConstraintLayout>

步骤3 − 将以下代码添加到AndroidManifest.xml

<?xml version = "1.0" encoding = "utf-8"?>
<manifest xmlns:android = "http://schemas.android.com/apk/res/android"
   package = "com.example.myapplication">
   <application
      android:allowBackup = "true"
      android:icon = "@mipmap/ic_launcher"
      android:label = "@string/app_name"
      android:roundIcon = "@mipmap/ic_launcher_round"
      android:supportsRtl = "true"
      android:theme = "@style/AppTheme">
      <activity android:name = ".SecondActivity">
      </activity>
      <activity android:name = ".MainActivity" android:configChanges = "keyboardHidden|orientation|screenSize">
         <intent-filter>
            <action android:name = "android.intent.action.MAIN" />
            <action android:name = "android.net.conn.CONNECTIVITY_CHANGE" />
            <category android:name = "android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

让我们尝试运行您的应用程序。我假设您已将实际的Android移动设备连接到计算机。要从Android Studio运行应用程序，请打开项目中的一个activity文件，然后单击运行工具栏中的图标。选择您的移动设备作为选项，然后检查您的移动设备，它将显示您的默认屏幕 –