我正在制作一个手电筒应用程序。该应用程序可以选择从后置摄像头闪光灯切换到前置摄像头闪光灯。问题是，当手电筒打开时，如果我将后置摄像头切换到前置，前置摄像头会闪烁不到一秒钟，然后关闭。有时这不会发生。所以，这是一个错误。我希望应用程序检查切换相机后手电筒是否保持打开状态。我想我必须使用火炬回调。但Google的文档描述性不够好，难以理解。而且，SO上对此没有太多讨论。所以，我不知道如何使用火炬回调。
package com.danielfernandzz.flashlight;
import android.content.Context;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CameraAccessException;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.Switch;
public class MainActivity extends AppCompatActivity {
public boolean switchState = false;
Button switchbutton;
String cameraId;
CameraManager camManager;
Switch frontToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
switchbutton = (Button) findViewById(R.id.Switch);
camManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
frontToggle = (Switch) findViewById(R.id.frontToggle);
try{cameraId = camManager.getCameraIdList()[0];}
catch (CameraAccessException ex){finish();}
}
public void switched(View v){
if(!switchState){
switchState = true;
switchbutton.setText("ON");
try {camManager.setTorchMode(cameraId,true);}
catch (CameraAccessException ex) {finish();}
}
else{
switchState = false;
switchbutton.setText("OFF");
try {camManager.setTorchMode(cameraId,false);}
catch (CameraAccessException ex) {finish();}
}
}
public void frontFlash(View z){
if (frontToggle.isChecked()){
if(switchState) {
try {camManager.setTorchMode(cameraId, false);}
catch (CameraAccessException ex) {finish();}
}
try{cameraId = camManager.getCameraIdList()[1];}
catch (CameraAccessException ex){finish();}
if(switchState) {
try {camManager.setTorchMode(cameraId, true);}
catch (CameraAccessException ex) {finish();}
}
//I want to add the callback to take place here
}
else {
if(switchState) {
try {camManager.setTorchMode(cameraId, false);}
catch (CameraAccessException ex) {finish();}
}
try{cameraId = camManager.getCameraIdList()[0];}
catch (CameraAccessException ex){finish();}
if(switchState) {
try {camManager.setTorchMode(cameraId, true);}
catch (CameraAccessException ex) {finish();}
}
//And here
}
}
}