问题
I am making a simple application that acts as a flashlight. I need to be able to turn on and off the flash from a button in the application with the Camera2 API, as I get errors with the old camera API. I would like to use a "torch" flashlight, where the camera doesn't have to open in order for the flash to turn on. I know it's possible, as lots of phones have a flash on/off in the quick settings menu, but I can't find any code or tutorials about how to do this.
Code:
Camera cam = Camera.open();
Parameters p = cam.getParameters();
p.setFlashMode(Parameters.FLASH_MODE_TORCH);
cam.setParameters(p);
cam.startPreview();
I am running on a Nexus 6P with Android 6.0.1.
EDIT: I need to use the Camera2 API. I haven't found a good tutorial for this yet, and after getting an answer, I will create one in Q/A format on here.
回答1:
I'll be addressing you to the Android Dev. documentation about the CameraManager since more code will be required but this is the basic code to activate the Flash on the camera in API's above 21.
CameraManager camManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
String cameraId = camManager.getCameraIdList()[0]; // Usually front camera is at 0 position.
camManager.setTorchMode(cameraId, true);
Android CameraManager documentation.
Android.hardware.camera2 documentation.
very important thing to remember that you will need to use try/catch to discard possible errors and ofcourse check that no other higher priority application is using the camera at the moment.
回答2:
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
mCameraManager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
try {
for (String camID : mCameraManager.getCameraIdList()) {
CameraCharacteristics cameraCharacteristics = mCameraManager.getCameraCharacteristics(camID);
int lensFacing = cameraCharacteristics.get(CameraCharacteristics.LENS_FACING);
if (lensFacing == CameraCharacteristics.LENS_FACING_FRONT && cameraCharacteristics.get(CameraCharacteristics.FLASH_INFO_AVAILABLE)) {
mCameraId = camID;
break;
} else if (lensFacing == CameraCharacteristics.LENS_FACING_BACK && cameraCharacteristics.get(CameraCharacteristics.FLASH_INFO_AVAILABLE)) {
mCameraId = camID;
}
}
if (mCameraId != null) {
mCameraManager.setTorchMode(mCameraId, true);
}
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
mCameraId will preferably turn on front camera flash by priority and if there is no front flash then back camera flash will be used. If device has no flash then mCameraId will be null and setTorchMode will not be called in the code above.
回答3:
Try this. Is working fine on me for android Pie and above. There is a toggle button that turns on and off the flashlight
ToggleButton FlB = (ToggleButton) findViewById(R.id.FlashBt);
final boolean[] IsTurnedOn = {false};
final CameraManager camManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
String cameraId = null; // Usually front camera is at 0 position.
try {
cameraId = camManager.getCameraIdList()[0];
} catch (CameraAccessException e) {
e.printStackTrace();
}
final String finalCameraId = cameraId;
FlB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (!IsTurnedOn[0]){
try {
camManager.setTorchMode(finalCameraId, true);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
else {
try {
camManager.setTorchMode(finalCameraId, false);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
IsTurnedOn[0] =!IsTurnedOn[0];
}
});
回答4:
Simplest and most banal way to do a flashlight app
// xml code
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.android.torcia.MainActivity">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ON"
android:id="@+id/flash_button"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"
android:onClick="turnOnOff"/>
</RelativeLayout>
//java code
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
Button flashButton;
String buttonText;
public void checkState(String buttonText) {
switch (buttonText) {
case "ON":
flashButton.setText("OFF");
flashOn();
break;
case "OFF":
flashButton.setText("ON");
flashOff();
break;
}
}
public void turnOnOff(View view) {
flashButton = (Button) findViewById(R.id.flash_button);
buttonText = flashButton.getText().toString();
checkState(this.buttonText);
}
public void flashOn() {
Camera camera = Camera.open();
Camera.Parameters parameters = camera.getParameters();
parameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
camera.setParameters(parameters);
camera.startPreview();
}
public void flashOff() {
Camera camera2 = Camera.open();
Camera.Parameters parameters2 = camera2.getParameters();
parameters2.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
camera2.setParameters(parameters2);
camera2.stopPreview();
}
}
// AndroidManifest
<?xml version="1.0" encoding="utf-8"?>
<uses-permission android:name="android.permission.CAMERA"/>
<uses-permission android:name="android.permission.FLASHLIGHT"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
来源：https://stackoverflow.com/questions/34699273/android-turn-on-off-camera-flash-programmatically-with-camera2