AndroidStudio学习（七)：调用摄像头拍照/从相册中选择照片
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2022-04-20 11:49:53
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教材：第一行代码（第2版）
新建项目CameraAlbumTest
调用摄像头拍照
//activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
//打开摄像头
<Button
android:id="@+id/take_photo"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Take Photo"
/>
//将拍到的图片显示出来
<ImageView
android:id="@+id/picture"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
/>
</LinearLayout>
//MainActivity
public class MainActivity extends AppCompatActivity {
private static final int TAKE_PHOTO = 1;
private ImageView picture;
private Uri imageUri;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button takePhoto = (Button) findViewById(R.id.take_photo);
picture = (ImageView) findViewById(R.id.picture);
takePhoto.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// 创建File对象，用于存储拍照后的图片
// 将图片命名为output_image.jpg，并将它存放在手机SD卡的应用关联缓存目录下
// getExternalCacheDir()可以得到这个目录
File outputImage = new File(getExternalCacheDir(),"output_image.jpg");
try {
if (outputImage.exists()){
outputImage.delete();
}
outputImage.createNewFile();
}catch (IOException e){
e.printStackTrace();
}
// 进行一个判断
// 如果运行设备的系统版本低于Android 7.0,就调用Uri的fromFile()方法将File对象转换成Uri对象
// 这个Uri对象标识着output_image.jpg这张图片的本地真实路径
// 否则，就调用FileProvider的getUriForFile()方法将File对象转换成一个封装过的Uri对象
// getUriForFile()方法接收 3个参数，第一个参数要求传入Context对象，第二个参数可以是任意唯一的字符串，第三个参数则是我们刚刚创建的File对象
// 之所以要进行这样一层转换，是因为从Android 7.0系统开始，直接使用本地真实路径的Uri被认为是不安全的，会抛出一个FileUriExposedException 异常
// 而FileProvider则是-种特殊的内容提供器，它使用了和内容提供器类似的机制来对数据进行保护，可以选择性地将封装过的Uri共享给外部，从而提高了应用的安全性
if (Build.VERSION.SDK_INT >= 24){
imageUri = FileProvider.getUriForFile(MainActivity.this, "com.example.cameraalbumtest.fileprovider", outputImage);
}else{
imageUri = Uri.fromFile(outputImage);
}
//启用相机程序
Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
startActivityForResult(intent, TAKE_PHOTO);
}
});
}
//报错 Overriding method should call super.onActivityResult
//不影响结果
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data){
switch (requestCode){
case TAKE_PHOTO:
if (resultCode == RESULT_OK){
try {
//将拍摄的照片显示出来
Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageUri));
picture.setImageBitmap(bitmap);
}catch (FileNotFoundException e){
e.printStackTrace();
}
}
break;
default:
break;
}
}
}
//在res目录下新建文件夹xml
//在xml下进行操作New→File
//命名为file_paths.xml
<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
<external-path //指定Uri共享
name="my_images" //自定义
path="" /> //path为空时表示将整个SD卡进行共享，这里会报错，不影响结果
</paths>
//AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.cameraalbumtest">
//声明访问SD卡的权限
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<application
......
//对内容提供器进行注册
<provider
android:name="androidx.core.content.FileProvider"
android:authorities="com.example.cameraalbumtest.fileprovider"
android:exported="false"
android:grantUriPermissions="true"
>
<meta-data
android:name="android.support.FILE_PROVIDER_PATHS"
android:resource="@xml/file_paths" />
</provider>
</application>
</manifest>
从相册中选择照片
//在activity_main.xml中添加代码
//注意：这个按钮控件在上两个控件之间
<Button
android:id="@+id/choose_from_album"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Choose From Album"
/>
//MainActivity
//添加代码
public class MainActivity extends AppCompatActivity {
......
public static final int CHOOSE_PHOTO = 2;
@Override
protected void onCreate(Bundle savedInstanceState) {
......
Button chooseFromAlbum = (Button) findViewById(R.id.choose_from_album);
//相机按钮
takePhoto.setOnClickListener(new View.OnClickListener() {
......
});
//照片按钮
chooseFromAlbum.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//动态申请读取SD卡权限
if(ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions(MainActivity.this, new String[]{ Manifest.permission.WRITE_EXTERNAL_STORAGE},1);
}else{
openAlbum();
}
}
});
}
private void openAlbum(){
Intent intent = new Intent("android.intent.action.GET_CONTENT");
intent.setType("image/*");
startActivityForResult(intent,CHOOSE_PHOTO); //打开相册
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults){
switch (requestCode){
case 1:
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
openAlbum();
}else{
Toast.makeText(this,"You denied the permission", Toast.LENGTH_SHORT).show();
}
break;
default:
}
}
//Overriding method should call super.onActivityResult
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data){
switch (requestCode){
case TAKE_PHOTO:
......
case CHOOSE_PHOTO:
if (resultCode == RESULT_OK){
//判断手机系统版本号
if (Build.VERSION.SDK_INT >= 19){
//4.4及以上系统使用这个方法处理图片
handleImageOnKitKat(data);
}else{
handleImageBeforeKitKat(data);
}
}
......
}
}
@TargetApi(19)
private void handleImageOnKitKat(Intent data){
String imagePath = null;
Uri uri = data.getData();
if(DocumentsContract.isDocumentUri(this,uri)){
/*如果是document类型的Uri，则通过document id处理*/
String docId = DocumentsContract.getDocumentId(uri);
if("com.android.providers.media.documents".equals(uri.getAuthority())){
String id = docId.split(":")[1]; //解析出数字格式的id
String selection = MediaStore.Images.Media._ID + "=" + id;
imagePath = getImagePath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,selection);
}else if("com.android.providers.downloads.documents".equals(uri.getAuthority())){
Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"),Long.valueOf(docId));
imagePath = getImagePath(contentUri,null);
}
}else if("content".equalsIgnoreCase(uri.getScheme())){
//如果是content类型的uri，则使用普通方式处理
imagePath = getImagePath(uri,null);
}else if("file".equalsIgnoreCase(uri.getScheme())){
//如果是file类型的uri，直接获取图片路径即可
imagePath = uri.getPath();
}
displayImage(imagePath); //根据图片路径显示图片
}
private void handleImageBeforeKitKat(Intent data){
Uri uri = data.getData();
String imagePath = getImagePath(uri,null);
displayImage(imagePath);
}
private String getImagePath(Uri uri,String selection){
String path = null;
//通过Uri和selection来获取真实的图片路径
Cursor cursor = getContentResolver().query(uri,null,selection,null,null);
if(cursor != null){
if (cursor.moveToFirst()){
path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
}
cursor.close();
}
return path;
}
private void displayImage(String imagePath){
if(imagePath != null){
Bitmap bitmap = BitmapFactory.decodeFile(imagePath);
picture.setImageBitmap(bitmap);
}else {
Toast.makeText(this,"failed to get image", Toast.LENGTH_SHORT).show();
}
}
}
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