Android学习笔记：获取相册和摄像机图片在APP显示Demo

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

三、在activity_main.xml布局文件内放置两个按钮和一个图像组件

<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/btLoadPicture"
android:text="LoadPicture"
android:onClick="onLoadPictureClick"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/btTakePicture"
android:text="TakePicture"
android:onClick="onTakePictureClick"/>

</LinearLayout>

<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/ivImage"/>

四、编写Main_Activity界面代码，如下：

package com.test.administrator.testpic;

import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;
import java.io.File;
import java.util.List;

public class MainActivity extends AppCompatActivity {
private static final int REQUEST_PICK_IMAGE = 1;
private static final int REQUEST_TAKE_PICTURE = 0;
ImageView imageView;
private File file;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = (ImageView) findViewById(R.id.ivImage);
}

public void onLoadPictureClick(View view) {
Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(intent, REQUEST_PICK_IMAGE);
}

public void onTakePictureClick(View view) {
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
file = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
file = new File(file, "picture.jpg");
intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(file));
if (isIntentAvailable(this, intent)) {
startActivityForResult(intent, REQUEST_TAKE_PICTURE);
} else {
Toast.makeText(this, "NoCameraAppsFound", Toast.LENGTH_SHORT).show();
}
}

private boolean isIntentAvailable(Context context, Intent intent) {
PackageManager packageManager = context.getPackageManager();
List<ResolveInfo> list = packageManager.queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);
return list.size() > 0;
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
Bitmap bitmap = null;
if(resultCode == RESULT_OK){
switch (requestCode){
case REQUEST_PICK_IMAGE:
Uri uri = data.getData();
String[] columns = {MediaStore.Images.Media.DATA};
Cursor cursor = getContentResolver().query(uri, columns, null, null, null);
if(cursor.moveToFirst()){
String imagePath = cursor.getString(0);
cursor.close();
bitmap = BitmapFactory.decodeFile(imagePath);

}
break;
case REQUEST_TAKE_PICTURE:
// Bitmap picture = (Bitmap) intent.getExtras().get("data");
bitmap = BitmapFactory.decodeFile(file.getPath());

break;
}
}
imageView.setImageBitmap(bitmap);
}
}

五、测试，如果是模拟机，必须在模拟机内放置图片，

注意的地方：我在测试代码的时候发现一个问题，在使用sdk版本为api23以上时，运行时会出现 permission denied错误，刚开始一直不知道原因在什么地方，出错的语句在

getContentResolver().query这个方法上，解决的方法是，采用api版本不能23以上，我用api22测试成功。