public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn= (Button) findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
                intent.setType("*/*");//设置类型，我这里是任意类型，任意后缀的可以这样写。
                intent.addCategory(Intent.CATEGORY_OPENABLE);
                startActivityForResult(intent,1);
            }
        });
    }
}

 intent.setType(“image/*”);
//intent.setType(“audio/*”); //选择音频
//intent.setType(“video/*”); //选择视频 （mp4 3gp 是android支持的视频格式）
//intent.setType(“video/*;image/*”);//同时选择视频和图片

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (resultCode == Activity.RESULT_OK) {//是否选择，没选择就不会继续
        Uri uri = data.getData();//得到uri，后面就是将uri转化成file的过程。
        String[] proj = {MediaStore.Images.Media.DATA};
        Cursor actualimagecursor = managedQuery(uri, proj, null, null, null);
        int actual_image_column_index = actualimagecursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        actualimagecursor.moveToFirst();
        String img_path = actualimagecursor.getString(actual_image_column_index);
        File file = new File(img_path);
        Toast.makeText(MainActivity.this, file.toString(), Toast.LENGTH_SHORT).show();
    }
}