调用系统的相册（展示图片）

添加权限

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

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

    <Button
        android:id="@+id/but"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:text="点击选择图片" />

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    //调用系统相册-选择图片
    private static final int IMAGE = 1;
    /**
     * 点击选择图片
     */
    private Button mBut;

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

    public void onClick(View v) {
        //调用相册
        Intent intent = new Intent(Intent.ACTION_PICK,
                MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
        startActivityForResult(intent, IMAGE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        //获取图片路径
        if (requestCode == IMAGE && resultCode == Activity.RESULT_OK && data != null) {
            Uri selectedImage = data.getData();
            String[] filePathColumns = {MediaStore.Images.Media.DATA};
            Cursor c = getContentResolver().query(selectedImage, filePathColumns, null, null, null);
            c.moveToFirst();
            int columnIndex = c.getColumnIndex(filePathColumns[0]);
            String imagePath = c.getString(columnIndex);
            showImage(imagePath);
            c.close();
        }
    }

    //加载图片
    private void showImage(String imaePath) {
        Bitmap bm = BitmapFactory.decodeFile(imaePath);
        ((ImageView) findViewById(R.id.image)).setImageBitmap(bm);
    }

    private void initView() {
        mBut = (Button) findViewById(R.id.but);
        mBut.setOnClickListener(this);
    }
}