进入android开发世界的所有初学者都应该构建一个简单的android应用程序,该应用程序可以通过单击按钮来打开/关闭手电筒或手电筒。因此,在本文结尾处,您将能够使用简单的布局构建自己的android手电筒应用程序。下面给出了一个示例GIF,以了解我们将在本文中做些什么。注意,我们将使用Java语言实现该项目。
构建简单的Flashlight / TorchLight Android应用程序的步骤
步骤1:创建一个新项目
要在Android Studio中创建新项目,请参阅如何在Android Studio中创建/启动新项目。请注意,选择Java作为编程语言。
步骤2:使用activity_main.xml
- 此布局包含一个简单的TextView,一个View(作为分隔线)和一个ToggleButton来切换Flashlight单元。
- 请参阅如何在Android应用程序中添加切换按钮,以实现并查看切换按钮的工作方式。
- 在activity_main.xml文件中调用以下代码,或者可以设计自定义窗口小部件。
XML
Java
import android.content.Context;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraManager;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
import android.widget.ToggleButton;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
private ToggleButton toggleFlashLightOnOff;
private CameraManager cameraManager;
private String getCameraID;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Register the ToggleButton with specific ID
toggleFlashLightOnOff = findViewById(R.id.toggle_flashlight);
// cameraManager to interact with camera devices
cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
// Exception is handled, because to check whether
// the camera resource is being used by another
// service or not.
try {
// O means back camera unit,
// 1 means front camera unit
getCameraID = cameraManager.getCameraIdList()[0];
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
// RequiresApi is set because, the devices which are
// below API level 10 don't have the flash unit with
// camera.
@RequiresApi(api = Build.VERSION_CODES.M)
public void toggleFlashLight(View view) {
if (toggleFlashLightOnOff.isChecked()) {
// Exception is handled, because to check
// whether the camera resource is being used by
// another service or not.
try {
// true sets the torch in ON mode
cameraManager.setTorchMode(getCameraID, true);
// Inform the user about the flashlight
// status using Toast message
Toast.makeText(MainActivity.this, "Flashlight is turned ON", Toast.LENGTH_SHORT).show();
} catch (CameraAccessException e) {
// prints stack trace on standard error
// output error stream
e.printStackTrace();
}
} else {
// Exception is handled, because to check
// whether the camera resource is being used by
// another service or not.
try {
// true sets the torch in OFF mode
cameraManager.setTorchMode(getCameraID, false);
// Inform the user about the flashlight
// status using Toast message
Toast.makeText(MainActivity.this, "Flashlight is turned OFF", Toast.LENGTH_SHORT).show();
} catch (CameraAccessException e) {
// prints stack trace on standard error
// output error stream
e.printStackTrace();
}
}
}
}
产生以下输出UI:
第3步:处理“切换按钮”小部件以在MainActivity内部切换“打开”或“关闭” 。 Java文件
MainActivity的完整代码。 Java文件如下。在代码内部添加了注释,以更详细地了解代码。
Java
import android.content.Context;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraManager;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
import android.widget.ToggleButton;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
private ToggleButton toggleFlashLightOnOff;
private CameraManager cameraManager;
private String getCameraID;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Register the ToggleButton with specific ID
toggleFlashLightOnOff = findViewById(R.id.toggle_flashlight);
// cameraManager to interact with camera devices
cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
// Exception is handled, because to check whether
// the camera resource is being used by another
// service or not.
try {
// O means back camera unit,
// 1 means front camera unit
getCameraID = cameraManager.getCameraIdList()[0];
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
// RequiresApi is set because, the devices which are
// below API level 10 don't have the flash unit with
// camera.
@RequiresApi(api = Build.VERSION_CODES.M)
public void toggleFlashLight(View view) {
if (toggleFlashLightOnOff.isChecked()) {
// Exception is handled, because to check
// whether the camera resource is being used by
// another service or not.
try {
// true sets the torch in ON mode
cameraManager.setTorchMode(getCameraID, true);
// Inform the user about the flashlight
// status using Toast message
Toast.makeText(MainActivity.this, "Flashlight is turned ON", Toast.LENGTH_SHORT).show();
} catch (CameraAccessException e) {
// prints stack trace on standard error
// output error stream
e.printStackTrace();
}
} else {
// Exception is handled, because to check
// whether the camera resource is being used by
// another service or not.
try {
// true sets the torch in OFF mode
cameraManager.setTorchMode(getCameraID, false);
// Inform the user about the flashlight
// status using Toast message
Toast.makeText(MainActivity.this, "Flashlight is turned OFF", Toast.LENGTH_SHORT).show();
} catch (CameraAccessException e) {
// prints stack trace on standard error
// output error stream
e.printStackTrace();
}
}
}
}
- 在此处阅读有关printStackTrace()函数的信息:带有示例的Java抛弃的printStackTrace()方法。
- 处理完ToggleButton之后,需要在物理android设备下测试该应用程序。因为如果您在android studio随附的仿真器中运行该应用程序,则单击ToggleButton时该应用程序将崩溃,因为该仿真器设备不会随相机闪光灯一起提供。
- 这种访问摄像机硬件的方法不需要用户的特殊许可即可访问摄像机单元。因为在这种情况下,我们仅通过相机ID(无论是前置摄像头还是后置摄像头)访问闪光灯。
应用程序UI的生成方式为:
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