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我学到书“6的Android Studio开发版纲要”第29" 章一个非常简单的动画样本,并得到一个错误的logcat的文件,如:setLayoutParams对空对象引用
显示java.lang.NullPointerException:试图调用虚拟方法“无效android.view.View.setLayoutParams(android.view.ViewGroup $的LayoutParams)”上的空对象引用被编译成功
我的样本代码,如下所示:
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;
import android.widget.Toast;
public class TransitionDemoActivity extends AppCompatActivity {
ViewGroup myLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_transition_demo);
myLayout=(ViewGroup)findViewById(R.id.myLayout);
myLayout.setOnTouchListener(
new RelativeLayout.OnTouchListener() {
public boolean onTouch(View v, MotionEvent m) {
handleTouch();
return true;
}
});
}
public void handleTouch() {
Toast.makeText(this,"Touching",Toast.LENGTH_LONG).show();//for listener test
View view = findViewById(R.id.myButton1);
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams
(RelativeLayout.LayoutParams.WRAP_CONTENT,
RelativeLayout.LayoutParams.WRAP_CONTENT);
params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT,
RelativeLayout.TRUE);
params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM,
RelativeLayout.TRUE);
**view.setLayoutParams(params);**
ViewGroup.LayoutParams lparams = view.getLayoutParams();
lparams.width = 500;
lparams.height = 350;
view.setLayoutParams(lparams);
}
}
我跟踪代码行找到“view.setLayoutParams(params)”上的错误代码位置,但我无法解决此问题。任何人都可以帮助我。 感谢
myButton1是在activity_transition_demo.xml中创建的,因此它被View view = findViewById(R.id.myButton1)引用; –
请将'activity_transition_demo.xml' – NoChinDeluxe