安卓学习

调用系统自带Carema
只需下面一行代码即可调用系统相机，相机拍照后会返回一个intent给onActivityResult。intent的extra部分包含一个编码过的Bitmap

Intent it = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);startActivityForResult(it,Activity.DEFAULT_KEYS_DIALER);//重写onActivityResult方法    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        if(requestCode == Activity.RESULT_OK){            Bundle bundle = data.getExtras();            Bitmap bitmap = (Bitmap) bundle.get("data");            img_show.setImageBitmap(bitmap);        }} 

拍完的图片是不会保存到本地的， 需要写代码把图片保存到我们的SD卡里，然后再显示，这样的图片会清晰很多

//定义一个保存图片的File变量private File currentImageFile = null;//在按钮点击事件处写上这些东西，这些是在SD卡创建图片文件的:            @Override            public void onClick(View v) {                File dir = new File(Environment.getExternalStorageDirectory(),"pictures");                if(dir.exists()){                    dir.mkdirs();                }                currentImageFile = new File(dir,System.currentTimeMillis() + ".jpg");                if(!currentImageFile.exists()){                    try {                        currentImageFile.createNewFile();                    } catch (IOException e) {                        e.printStackTrace();                    }                }                Intent it = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);                it.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(currentImageFile));                startActivityForResult(it, Activity.DEFAULT_KEYS_DIALER);            }//onActivityResult： @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        if (requestCode == Activity.DEFAULT_KEYS_DIALER) {        img_show.setImageURI(Uri.fromFile(currentImageFile));        }}

拍照页面
布局代码：activity_main.xml：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <SurfaceView        android:id="@+id/sfv_preview"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_weight="1" />    <Button        android:id="@+id/btn_take"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="调用系统照相机" /></LinearLayout>

MainActivity.java：

public class MainActivity extends AppCompatActivity {    private SurfaceView sfv_preview;    private Button btn_take;    private Camera camera = null;    private SurfaceHolder.Callback cpHolderCallback = new SurfaceHolder.Callback() {        @Override        public void surfaceCreated(SurfaceHolder holder) {            startPreview();        }        @Override        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {        }        @Override        public void surfaceDestroyed(SurfaceHolder holder) {            stopPreview();        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        bindViews();    }    private void bindViews() {        sfv_preview = (SurfaceView) findViewById(R.id.sfv_preview);        btn_take = (Button) findViewById(R.id.btn_take);        sfv_preview.getHolder().addCallback(cpHolderCallback);        btn_take.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                camera.takePicture(null, null, new Camera.PictureCallback() {                    @Override                    public void onPictureTaken(byte[] data, Camera camera) {                        String path = "";                        if ((path = saveFile(data)) != null) {                            Intent it = new Intent(MainActivity.this, PreviewActivity.class);                            it.putExtra("path", path);                            startActivity(it);                        } else {                            Toast.makeText(MainActivity.this, "保存照片失败", Toast.LENGTH_SHORT).show();                        }                    }                });            }        });    }    //保存临时文件的方法    private String saveFile(byte[] bytes){        try {            File file = File.createTempFile("img","");            FileOutputStream fos = new FileOutputStream(file);            fos.write(bytes);            fos.flush();            fos.close();            return file.getAbsolutePath();        } catch (IOException e) {            e.printStackTrace();        }        return "";    }    //开始预览    private void startPreview(){        camera = Camera.open();        try {            camera.setPreviewDisplay(sfv_preview.getHolder());            camera.setDisplayOrientation(90);   //让相机旋转90度            camera.startPreview();        } catch (IOException e) {            e.printStackTrace();        }    }    //停止预览    private void stopPreview() {        camera.stopPreview();        camera.release();        camera = null;    }}

将图片显示到界面上，PreviewActivity.java：

public class PreviewActivity extends AppCompatActivity {    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        ImageView img = new ImageView(this);        String path = getIntent().getStringExtra("path");        if(path != null){            img.setImageURI(Uri.fromFile(new File(path)));        }        setContentView(img);    }}

权限:

<uses-permission android:name="android.permission.CAMERA"/><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>