如何在没有输入数据的情况下更改活动？

Question

我正在尝试使用意图将输入数据传递给另一个活动。 顺便说一句，它运行良好，但是当我尝试在没有任何输入数据的情况下更改活动时，应用程序会关闭。 如何在没有输入数据和图像文件的情况下更改活动？

这是上传活动代码：

imageView = (ImageView) findViewById(R.id.imageview);
    Button uploading = (Button) findViewById(R.id.upload_upload);
    uploading.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            ByteArrayOutputStream stream = new ByteArrayOutputStream();
            Bitmap bitmap = ((BitmapDrawable)imageView.getDrawable()).getBitmap();
            float scale = (float) (1024/(float)bitmap.getWidth());
            int image_w = (int) (bitmap.getWidth() * scale);
            int image_h = (int) (bitmap.getHeight() * scale);
            Bitmap resize = Bitmap.createScaledBitmap(bitmap, image_w, image_h, true);
            resize.compress(Bitmap.CompressFormat.JPEG, 100, stream);
            byte[] byteArray = stream.toByteArray();

            Intent intent = new Intent(upload.this,MainActivity.class);

            intent.putExtra("integer", 300);
            intent.putExtra("double", 3.141592);
            intent.putExtra("image", byteArray);


            EditText input_title = (EditText) findViewById(R.id.upload_title);
            String temp1 = input_title.getText().toString();
            intent.putExtra("temp1",temp1);

            EditText input_author = (EditText) findViewById(R.id.upload_author);
            String temp2 = input_author.getText().toString();
            intent.putExtra("temp2",temp2);
            
            startActivity(intent);
        }
    });

主要活动代码：

ImageView imageView = (ImageView) findViewById(R.id.main_image);

    Bundle extras = getIntent().getExtras();
    byte[] byteArray = getIntent().getByteArrayExtra("image");
    Bitmap bitmap = BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);

    imageView.setImageBitmap(bitmap);

    text_title = (TextView) findViewById(R.id.title); 

    Intent receiver = getIntent();

    String title_temp = receiver.getStringExtra("temp1");
    text_title.setText(title_temp);

    text_author = (TextView)  findViewById(R.id.author);

    String author_temp = receiver.getStringExtra("temp2");
    text_author.setText(author_temp);

Answer 1

您没有添加任何崩溃日志，但是通过查看您的代码，我发现您没有验证 Intent extras 不是 null。 这可能会导致 NullPointerException 并且绝对可能是崩溃的原因。

在使用 Intent 之前添加一个 null 检查：

Bundle extras = getIntent().getExtra();
if (extras != null) {
    ImageView imageView = (ImageView) findViewById(R.id.main_image);

    byte[] byteArray = receiver.getByteArrayExtra("image");
    Bitmap bitmap = BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);

    imageView.setImageBitmap(bitmap);

    text_title = (TextView) findViewById(R.id.title); 


    String title_temp = receiver.getStringExtra("temp1");
    text_title.setText(title_temp);

    text_author = (TextView)  findViewById(R.id.author);

    String author_temp = receiver.getStringExtra("temp2");
    text_author.setText(author_temp);
}

Answer 2

您必须通过以下检查检查您的意图是否有额外内容，否则它会抛出 NullpointerExxception。 如果意图有额外的，它只会设置值

   if (receiver.getExtras() != null){
    
    String title_temp = receiver.getStringExtra("temp1");
    text_title.setText(title_temp);

    text_author = (TextView)  findViewById(R.id.author);

    String author_temp = receiver.getStringExtra("temp2");
    text_author.setText(author_temp);
}

或者您也可以通过此检查特定的附加功能

    if (receiver.getExtras() != null && receiver.getExtras().containsKey("temp1")) {
        String title_temp = receiver.getStringExtra("temp1");
        text_title.setText(title_temp);
    }