英文:
i am getting a null object reference error in android studio while animating a image
问题
public class MainActivity extends AppCompatActivity {
public void click(View view) {
ImageView bart = (ImageView) findViewById(R.drawable.bart);
bart.animate().alpha(0);
}
}
这是错误信息：
Caused by: java.lang.NullPointerException: 尝试在空对象引用上调用虚拟方法 'android.view.ViewPropertyAnimator android.widget.ImageView.animate()'
英文:
public class MainActivity extends AppCompatActivity {
public void click(View view) {
ImageView bart = (ImageView) findViewById(R.drawable.bart);
bart.animate().alpha(0);
}
}
This is the error
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewPropertyAnimator android.widget.ImageView.animate()' on a null object reference
答案1
得分: 1
似乎你在引用一个“drawable id”，而不是一个“view id”。
对于视图，请使用R.id，而对于可绘制资源，请使用R.drawable。
英文:
It seems that you are referencing to a drawable id and not a view id.
Use R.id for views, R.drawable is for drawable resource.
答案2
得分: 1
从：
R.drawable.bart
变成：
R.id.bart
并且你确定在 onCreate() 方法中调用了 setContentView() 方法（用于填充布局）吗？
英文:
Change from:
R.drawable.bart
in to:
R.id.bart
And are you sure that in onCreate() you call setContentView() method (which inflates layout)?
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