Question

这是 MainActivity.java。应用程序包含一个带有ImageView和Button的活动。点按这些按钮时，图库必须打开。之后，您将检查粘贴在ImageView中的一些图像。想要退出应用程序或点按时，我无法将图像保存在活动中。

import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    static final int GALLERY_REQUEST = 1;

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

        Button button = (Button)findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Intent photoPickerIntent = new Intent(Intent.ACTION_PICK);
                photoPickerIntent.setType("image/*");
                startActivityForResult(photoPickerIntent, GALLERY_REQUEST);
            }
        });
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent imageReturnedIntent) {
        super.onActivityResult(requestCode, resultCode, imageReturnedIntent);

        Bitmap bitmap = null;
        ImageView imageView = (ImageView) findViewById(R.id.imageView);

        switch(requestCode) {
            case GALLERY_REQUEST:
                if(resultCode == RESULT_OK){
                    Uri selectedImage = imageReturnedIntent.getData();
                    try {
                        bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), selectedImage);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    imageView.setImageBitmap(bitmap);
                    super.onResume();
                }
        }
    }}

这是 content_main.xml。这里我创建了一个按钮和空ImageView，用于粘贴图库中的图像。请告诉我们如何在活动中保存图像和文字。

Answer 1

当活动关闭时，它将被销毁。您应该将数据保存在某处，然后将其还原。例如，在SharedPreferences中。最简单的方法如下所示。

public class MainActivity extends AppCompatActivity {

    static final int GALLERY_REQUEST = 1;

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

        Button button = (Button)findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Intent photoPickerIntent = new Intent(Intent.ACTION_PICK);
                photoPickerIntent.setType("image/*");
                startActivityForResult(photoPickerIntent, GALLERY_REQUEST);
            }
        });

        SharedPreferences preferences = getPreferences(MODE_PRIVATE);
        String uriString = preferences.getString("MainPicture", null);

        if (uriString != null) {
            Bitmap bitmap = null;
            ImageView imageView = (ImageView) findViewById(R.id.imageView);
            Uri selectedImage = Uri.parse(uriString);
            try {
                bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), selectedImage);
                SharedPreferences.Editor editor = getPreferences(MODE_PRIVATE).edit();
                editor.putString("MainPicture", selectedImage.toString());
                editor.apply();
            } catch (IOException e) {
                e.printStackTrace();
            }
            imageView.setImageBitmap(bitmap);
        }
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent imageReturnedIntent) {
        super.onActivityResult(requestCode, resultCode, imageReturnedIntent);

        Bitmap bitmap = null;
        ImageView imageView = (ImageView) findViewById(R.id.imageView);

        switch(requestCode) {
            case GALLERY_REQUEST:
                if(resultCode == RESULT_OK){
                    Uri selectedImage = imageReturnedIntent.getData();
                    try {
                        bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), selectedImage);
                        SharedPreferences.Editor editor = getPreferences(MODE_PRIVATE).edit();
                        editor.putString("MainPicture", selectedImage.toString());
                        editor.apply();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    imageView.setImageBitmap(bitmap);
                    super.onResume();
                }
        }
    }}

为什么不退出从库中加载的Activity中的imageView，退出或点击后退？

1 个答案: