如何从 Android 中的图库中选择图像?
当用户必须上传或将他们的图像设置为个人资料图片或用户想要向另一个人发送图片时,需要从 Android 中的图库中选择一个图像。因此,在本文中,逐步讨论了如何从图库中选择图像并预览所选图像。请看下图,本文进一步讨论了哪些内容。
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从图库中实现图像选择的步骤
第 1 步:创建一个空的活动项目
- 创建一个空的活动 Android Studio 项目。并选择Java作为编程语言。
- 参考安卓 |如何在 Android Studio 中创建/启动新项目?了解如何创建一个空的活动 Android Studio 项目。
第 2 步:使用 activity_main.xml
- 该应用程序的主要布局包括一个用于打开图像选择器的按钮,以及一个用于从图库中预览所选图像的图像视图。
- 要实现应用程序的布局,请调用activity_main.xml文件中的以下代码。
XML
Java
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
public class MainActivity extends AppCompatActivity {
// One Button
Button BSelectImage;
// One Preview Image
ImageView IVPreviewImage;
// constant to compare
// the activity result code
int SELECT_PICTURE = 200;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// register the UI widgets with their appropriate IDs
BSelectImage = findViewById(R.id.BSelectImage);
IVPreviewImage = findViewById(R.id.IVPreviewImage);
// handle the Choose Image button to trigger
// the image chooser function
BSelectImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
imageChooser();
}
});
}
// this function is triggered when
// the Select Image Button is clicked
void imageChooser() {
// create an instance of the
// intent of the type image
Intent i = new Intent();
i.setType("image/*");
i.setAction(Intent.ACTION_GET_CONTENT);
// pass the constant to compare it
// with the returned requestCode
startActivityForResult(Intent.createChooser(i, "Select Picture"), SELECT_PICTURE);
}
// this function is triggered when user
// selects the image from the imageChooser
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK) {
// compare the resultCode with the
// SELECT_PICTURE constant
if (requestCode == SELECT_PICTURE) {
// Get the url of the image from data
Uri selectedImageUri = data.getData();
if (null != selectedImageUri) {
// update the preview image in the layout
IVPreviewImage.setImageURI(selectedImageUri);
}
}
}
}
}
输出界面:
第 3 步:使用 MainActivity。 Java文件
- 在这种情况下,imageChooser 被触发,意图是“图像”类型,动作为ACTION_GET_CONTENT。
- 调用以下代码来实现相同的功能。添加注释以便更好地理解。
Java
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
public class MainActivity extends AppCompatActivity {
// One Button
Button BSelectImage;
// One Preview Image
ImageView IVPreviewImage;
// constant to compare
// the activity result code
int SELECT_PICTURE = 200;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// register the UI widgets with their appropriate IDs
BSelectImage = findViewById(R.id.BSelectImage);
IVPreviewImage = findViewById(R.id.IVPreviewImage);
// handle the Choose Image button to trigger
// the image chooser function
BSelectImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
imageChooser();
}
});
}
// this function is triggered when
// the Select Image Button is clicked
void imageChooser() {
// create an instance of the
// intent of the type image
Intent i = new Intent();
i.setType("image/*");
i.setAction(Intent.ACTION_GET_CONTENT);
// pass the constant to compare it
// with the returned requestCode
startActivityForResult(Intent.createChooser(i, "Select Picture"), SELECT_PICTURE);
}
// this function is triggered when user
// selects the image from the imageChooser
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK) {
// compare the resultCode with the
// SELECT_PICTURE constant
if (requestCode == SELECT_PICTURE) {
// Get the url of the image from data
Uri selectedImageUri = data.getData();
if (null != selectedImageUri) {
// update the preview image in the layout
IVPreviewImage.setImageURI(selectedImageUri);
}
}
}
}
}