findviewbyid

问题 Recently i found that AndroidStudio reminds me to remove some class cast. I remember that in the old time, we have to cast the result of findViewById, but now it\'s not necessary. The result of findViewById is still View, so i want to know why we don\'t need to cast the class? I can\'t find any documents mentioned that, can anyone find any document? 回答1: Starting with API 26, findViewById uses inference for its return type, so you no longer have to cast. Old definition: View findViewById(int

问题 I cannot find a TextView by calling findViewById() , even though the ID does exist. OtherActivity : public class OtherActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { TextView textView = (TextView)findViewById(R.ID.txt02); super.onCreate(savedInstanceState);//line 5 setContentView(R.layout.other_activity); //textView.setText(ACCESSIBILITY_SERVICE); Button button = (Button)findViewById(R.ID.otherActivity_Btn); button.setText(R.string.otherActivityBtn);

问题 I was just testing input/output, there was no special purpose, this is the last code that had run successfully: public class MainActivity extends AppCompatActivity { /* EditText username = (EditText)findViewById(R.id.editText_Username); EditText password = (EditText)findViewById(R.id.editText_Password); TextView inputdata = (TextView)findViewById(R.id.textView_InputData); TextView welcome = (TextView)findViewById(R.id.textView_Welcome); Button login=(Button)findViewById(R.id.button_Login);

问题 I am trying to create an ImageView in a Fragment which will refer to the ImageView element which I have created in the XML for the Fragment. However, the findViewById method only works if I extend an Activity class. Is there anyway of which I can use it in Fragment as well? public class TestClass extends Fragment { public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { ImageView imageView = (ImageView)findViewById(R.id.my_image); return inflater

问题 In an XML file, we can assign an ID to a view like android:id=\"@+id/something\" and then call findViewById() , but when creating a view programmatically, how do I assign an ID? I think setId() is not the same as default assignment. setId() is extra. Can anybody correct me? 回答1: Android id overview An Android id is an integer commonly used to identify views; this id can be assigned via XML (when possible) and via code (programmatically.) The id is most useful for getting references for XML

问题 Can anyone help me to find out what can be the issue with this program. In the onCreate() method the findViewById() returns null for all ids and this causes a null pointer exception later. I can not figure out why the findViewById() can not find the view. Any suggestions? This is the main code: public class MainActivity extends Activity { ViewPager pager; MyPagerAdapter adapter; LinearLayout layout1, layout2, layout3; @Override protected void onCreate(Bundle savedInstanceState) { super

问题 When my SplashActivity opens the LoginActivity my app crashes. The following is my SplashActivity.java : package com.example.android.appName; import android.content.Intent; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import java.util.Timer; import java.util.TimerTask; public class SplashActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_splash);