如何在 Android 中管理 startActivityForResult?
androidmobile developmentapps/applications
本示例演示如何在 Android 中管理 startActivityForResult。
步骤 1 - 在 Android Studio 中创建一个新项目，依次点击"文件">"新建项目"，并填写所有必需信息以创建一个新项目。
步骤 2 - 将以下代码添加到 res/layout/activity_main.xml 文件中。
<?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，我们使用文本视图来显示活动结果数据。
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 - 添加以下代码 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 - 在 AndroidManifest.xml 文件中添加以下代码
<?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 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，然后单击工具栏中的"运行"图标。选择您的移动设备作为选项，然后选中您的移动设备，它将显示您的默认屏幕 –
现在点击文本视图，它会从第二个活动获取数据并显示如下所示的结果 -
