前言：我把我的安卓手机恢复出厂设置以后，手电筒这个软件莫名消失了，想要从应用市场下载一个使用，发现都有广告，那么只好手写一个了。

点击下方链接下载手电筒app：

https://download.csdn.net/download/sinat_30949835/12630516

源码分享：

MainActivity.java

package com.lnkjly.shoudiantong;

import androidx.annotation.NonNull;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;

import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.Camera;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraManager;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    private Button button;
    private CameraManager mCameraManager;
    private boolean isFlashLightOn = false;

    @TargetApi(Build.VERSION_CODES.M)
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        button = (Button) findViewById(R.id.btn_sdt);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                toggleLight(!isFlashLightOn);
            }
        });
        //获取CameraManager
        if(mCameraManager == null){
            mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        }
        mCameraManager.registerTorchCallback(mTorchCallback, null);
    }

    @TargetApi(Build.VERSION_CODES.M)
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private CameraManager.TorchCallback mTorchCallback = new CameraManager.TorchCallback() {
        @Override
        public void onTorchModeChanged(@NonNull String cameraId, boolean enabled) {
            super.onTorchModeChanged(cameraId, enabled);
//            Log.Loge(TAG, "onTorchModeChanged cameraId=" + cameraId + ";enabled=" + enabled);
            isFlashLightOn = enabled;
//            ivFlashlight.setIcon(enabled ? MaterialDrawableBuilder.IconValue.FLASHLIGHT : MaterialDrawableBuilder.IconValue.FLASHLIGHT_OFF);
        }
    };

    @TargetApi(Build.VERSION_CODES.M)
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public void toggleLight(boolean OPEN) {
        try {
            //获取当前手机所有摄像头设备ID
            String[] ids = mCameraManager.getCameraIdList();
            for (String id : ids) {
                CameraCharacteristics c = mCameraManager.getCameraCharacteristics(id);
                //查询该摄像头组件是否包含闪光灯
                Boolean flashAvailable = c.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);

                
                Integer lensFacing = c.get(CameraCharacteristics.LENS_FACING);
                if (flashAvailable != null && flashAvailable
                        && lensFacing != null && lensFacing == CameraCharacteristics.LENS_FACING_BACK) {
                    //打开或关闭手电筒
                    mCameraManager.setTorchMode(id, OPEN);
                    break;
                }
            }
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    @RequiresApi(api = Build.VERSION_CODES.M)
    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(mCameraManager != null && mTorchCallback != null){
            mCameraManager.unregisterTorchCallback(mTorchCallback);
        }
    }
}

app/src/main/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:layout_height="match_parent"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:gravity="center"
        >
        <View
            android:layout_weight="1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            />
        <Button
            android:id="@+id/btn_sdt"
            android:layout_width="300dp"
            android:layout_height="300dp"
            android:text="手电筒"
            android:layout_marginBottom="50dp"
            />
    </LinearLayout>

</LinearLayout>

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 29
    defaultConfig {
        applicationId "com.lnkjly.shoudiantong"
        minSdkVersion 19
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}

logo的话随便找一个就可以了。

通过以上代码就可以完成最简单的一个手电筒应用哦。