Androidは懐中電灯の機能をオンにします。（Android 4 x、5 x、6 xにぴったりです。）

<uses-permission android:name="android.permission.FLASHLIGHT" />
    <uses-permission android:name="android.permission.CAMERA" />
    <uses-feature android:name="android.hardware.camera" />
    <uses-feature android:name="android.hardware.autofocus" />

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical">

    <Button  android:id="@+id/btn_open" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginBottom="10dp" android:text="     " />

    <Button  android:id="@+id/btn_close" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="     " />
</LinearLayout>

/** * Created by        Castiel *     ：http://blog.csdn.net/mynameishuangshuai */

public class MainActivity extends AppCompatActivity {
    private CameraManager manager;//   CameraManager  
    private Camera m_Camera = null;//   Camera  

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btnOpen = (Button) findViewById(R.id.btn_open);
        Button btnClose = (Button) findViewById(R.id.btn_close);
        manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        try {
            String[] camerList = manager.getCameraIdList();
            for (String str : camerList) {
            }
        } catch (CameraAccessException e) {
            Log.e("error", e.getMessage());
        }

        btnOpen.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                lightSwitch(false);
            }
        });

        btnClose.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                lightSwitch(true);
            }
        });
    }

    /** *         * * @param lightStatus * @return */
    private void lightSwitch(final boolean lightStatus) {
        if (lightStatus) { //      
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                try {
                    manager.setTorchMode("0", false);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            } else {
                if (m_Camera != null) {
                    m_Camera.stopPreview();
                    m_Camera.release();
                    m_Camera = null;
                }
            }
        } else { //      
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                try {
                    manager.setTorchMode("0", true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            } else {
                final PackageManager pm = getPackageManager();
                final FeatureInfo[] features = pm.getSystemAvailableFeatures();
                for (final FeatureInfo f : features) {
                    if (PackageManager.FEATURE_CAMERA_FLASH.equals(f.name)) { //            
                        if (null == m_Camera) {
                            m_Camera = Camera.open();
                        }
                        final Camera.Parameters parameters = m_Camera.getParameters();
                        parameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
                        m_Camera.setParameters(parameters);
                        m_Camera.startPreview();
                    }
                }
            }
        }
    }


    /** *   Android       >= M(API23) */
    private boolean isM() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            return true;
        } else {
            return false;
        }
    }
}