Android 放大镜效果实现

放大镜就是直接调用相机，使用放大缩小的功能实现，调用相机有两种方式，一种是直接调用系统的；另一种是自定义相机，需要自定义一个预览界面，下面简单介绍自定义相机方式：
参考:http://developer./guide/topics/media/camera.html
首先我们需要申请权限：
1、获取需要的权限，检测手机是否有相机。

//manifest里添加使用相机的权限

<uses-permission android:name="android.permission.CAMERA" />
//使用相机属性
<uses-feature android:name="android.hardware.camera" />
//相机自动对焦
<uses-feature android:name="android.hardware.camera.autofocus" />
1
2
3
4
5
6
7
1
2
3
4
5
6
7

然后再判断是否有相机存在：

/** Check if this device has a camera */
private boolean checkCameraHardware(Context context) {
    if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
        // this device has a camera
        return true;
    } else {
        // no camera on this device
        return false;
    }
}
1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
10

2.打开相机，官网实现的安全方式打开相机

/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
    Camera c = null;
    try {
        c = Camera.open(); // attempt to get a Camera instance
    }
    catch (Exception e){
        // Camera is not available (in use or does not exist)
    }
    return c; // returns null if camera is unavailable
}
1
2
3
4
5
6
7
8
9
10
11
1
2
3
4
5
6
7
8
9
10
11

3、创建预览窗口，这是最主要的部分
SurfaceView：该类是一个视图组件，实现了照片的预览功能。
SurfaceHolder：一个抽象接口，是SurfaceView的支持类，一般通过SurfaceView的getHolder()方法获得。允许你控制界面的尺寸和格式、编辑界面的像素，以及监控界面尺寸的改变。
SurfaceHolder.Callback：SurfaceHolder 的一个内部接口，可以实现该接口获取界面改变的信息。该接口中有三个方法，surfaceCreated()方法在界面创建时被调用，一般在该方法中打开 照相机并设置预览。surfaceChanged()方法在界面尺寸改变时 被调用，一般在该方法中设置相机的参数（大小、格式等）。 surfaceDestroyed()方法在界面被销毁时调用，在该方法中清除相机实例，释放资源。
Camera：相机类，实现拍照功能。
Camera.PictureCallback：Camera的一个内部接口，处理照片准备好后的回调。
接着我们定义预览窗口的自定义View

/** A basic Camera preview class */
    public class MyPreview extends SurfaceView implements SurfaceHolder.Callback {
        private SurfaceHolder mHolder;
        private Camera mCamera;

        public MyPreview(Context context, Camera camera) {
            super(context);
            mCamera = camera;

            // Install a SurfaceHolder.Callback so we get notified when the
            // underlying surface is created and destroyed.
            mHolder = getHolder();
            mHolder.addCallback(this);
            // deprecated setting, but required on Android versions prior to 3.0
            mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        }

        public void surfaceCreated(SurfaceHolder holder) {
            // The Surface has been created, now tell the camera where to draw the preview.
            //获取相机属性
            Camera.Parameters parameters = mCamera.getParameters();
            //自动对焦
            parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
            //由于相机默认是横屏的，创建时旋转一下调正位置
            if(this.getResources().getConfiguration().orientation!= Configuration.ORIENTATION_LANDSCAPE){
                parameters.set("orientation", "portrait");
                mCamera.setDisplayOrientation(90);
                parameters.setRotation(90);
            }else{
                parameters.set("orientation", "landscape");
                mCamera.setDisplayOrientation(0);
                parameters.setRotation(0);
            }
            mCamera.setParameters(parameters);
            try {
                mCamera.setPreviewDisplay(holder);
                mCamera.startPreview();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        public void surfaceDestroyed(SurfaceHolder holder) {
            // empty. Take care of releasing the Camera preview in your activity.
        }

        public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
            // If your preview can change or rotate, take care of those events here.
            // Make sure to stop the preview before resizing or reformatting it.

            if (mHolder.getSurface() == null){
                // preview surface does not exist
                return;
            }

            // stop preview before making changes
            try {
                mCamera.stopPreview();
            } catch (Exception e){
                // ignore: tried to stop a non-existent preview
            }

            // make any resize, rotate or reformatting changes here

            // start preview with new settings
            try {
                mCamera.setPreviewDisplay(mHolder);
                mCamera.startPreview();

            } catch (Exception e){
                e.printStackTrace();
            }
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
//            return super.onTouchEvent(event);
            //按下时自动对焦
            if (event.getAction() == MotionEvent.ACTION_DOWN) {
                mCamera.autoFocus(null);
            }
            return true;

        }
    }
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85

4、添加seekbar调节预览区域的缩放。
由于在Nexus5上获取到的maxZoom是99，如果你的设备取不到这么大，那么需要将progress的刻度乘一个比例，以免报错。

   /**
         * maxZoom = parameters.getMaxZoom(); 最大缩放
         * ratio = 100 / maxZoom；获取比例
         */
        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            Camera c = mCamera;
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                if(progress / ratio < maxZoom)
                    parameters.setZoom(progress / ratio);
                c.setParameters(parameters);
                c.autoFocus(null);
            }
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
3
4
5
6
7
8
9
10
11
12
13

下面是Demo的核心部分代码：

public class MainActivity extends Activity {

    private Camera mCamera;
    private CameraPreview mPreview;
    private boolean isClicked = false;
    private Camera.AutoFocusCallback mAutoFocusCallback;
    private SeekBar seekBar;
    private int maxZoom;
    private int ratio = 1;
    Camera.Parameters parameters;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        seekBar = (SeekBar)findViewById(R.id.seekBar);
            mCamera = safeCameraOpen();
        mAutoFocusCallback = new Camera.AutoFocusCallback() {
            public void onAutoFocus(boolean success, Camera camera) {
                Camera c=mCamera;
                // TODO Auto-generated method stub
                if(success){
                //自动对焦成功
                    c.setOneShotPreviewCallback(null);

            }
        };
        if(mCamera != null) {
            mPreview = new CameraPreview(this, mCamera);
            FrameLayout preview = (FrameLayout) findViewById(R.id.framelayout);
            preview.addView(mPreview);
            parameters = mCamera.getParameters();
            maxZoom = parameters.getMaxZoom();
            if(maxZoom > 0)
                ratio = 100 / maxZoom;
//            parameters.setZoom(99);
//            mCamera.setParameters(parameters);
        }

        /**
         * maxZoom = parameters.getMaxZoom(); 最大缩放
         * ratio = 100 / maxZoom；获取比例
         */
        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            Camera c = mCamera;
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                if(progress / ratio < maxZoom)
                    parameters.setZoom(progress / ratio);
                c.setParameters(parameters);
                c.autoFocus(null);
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

            }
        });
    }
    @Override
    protected void onPause() {
        super.onPause();
        if(mCamera != null){
            mCamera.release();
        }
    }

    @Override
    protected void onResume(){
        super.onResume();
        mCamera = safeCameraOpen();
    }

    //camera
    private Camera safeCameraOpen() {
        Camera c = null;
        try {
            c = Camera.open();
        } catch (Exception e) {
            Log.e(getString(R.string.app_name), "failed to open Camera");
            e.printStackTrace();
        }

        return c;
    }
    //自定义相机展览区
    public class MyPreview extends SurfaceView implements SurfaceHolder.Callback {
        private SurfaceHolder mHolder;
        private Camera mCamera;

        public MyPreview(Context context, Camera camera) {
            super(context);
            mCamera = camera;

            // Install a SurfaceHolder.Callback so we get notified when the
            // underlying surface is created and destroyed.
            mHolder = getHolder();
            mHolder.addCallback(this);
            // deprecated setting, but required on Android versions prior to 3.0
            mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        }

        public void surfaceCreated(SurfaceHolder holder) {
            // The Surface has been created, now tell the camera where to draw the preview.
            //获取相机属性
            Camera.Parameters parameters = mCamera.getParameters();
            //自动对焦
            parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
            //由于相机默认是横屏的，创建时旋转一下调正位置
            if(this.getResources().getConfiguration().orientation!= Configuration.ORIENTATION_LANDSCAPE){
                parameters.set("orientation", "portrait");
                mCamera.setDisplayOrientation(90);
                parameters.setRotation(90);
            }else{
                parameters.set("orientation", "landscape");
                mCamera.setDisplayOrientation(0);
                parameters.setRotation(0);
            }
            mCamera.setParameters(parameters);
            try {
                mCamera.setPreviewDisplay(holder);
                mCamera.startPreview();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        public void surfaceDestroyed(SurfaceHolder holder) {
            // empty. Take care of releasing the Camera preview in your activity.
        }

        public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
            // If your preview can change or rotate, take care of those events here.
            // Make sure to stop the preview before resizing or reformatting it.

            if (mHolder.getSurface() == null){
                // preview surface does not exist
                return;
            }

            // stop preview before making changes
            try {
                mCamera.stopPreview();
            } catch (Exception e){
                // ignore: tried to stop a non-existent preview
            }

            // make any resize, rotate or reformatting changes here

            // start preview with new settings
            try {
                mCamera.setPreviewDisplay(mHolder);
                mCamera.startPreview();

            } catch (Exception e){
                e.printStackTrace();
            }
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
//            return super.onTouchEvent(event);
            //按下时自动对焦
            if (event.getAction() == MotionEvent.ACTION_DOWN) {
                mCamera.autoFocus(null);
            }
            return true;

        }
    }

    /** Check if this device has a camera */
    private boolean checkCameraHardware(Context context) {
        if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
            // this device has a camera
            return true;
        } else {
            // no camera on this device
            return false;
        }
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188