[英]Android setOnClickListener not working
在android中添加按钮动作后,Activity.java应用程序不幸关闭。 请帮助解决。 我在这里缺少什么代码????
public class MainActivity extends ActionBarActivity {
int counter;
Button add, sub;
TextView display;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
counter = 0;
add = (Button) findViewById(R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.textDisp);
add.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Perform action on click
counter++;
}
});
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment())
.commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
return rootView;
}
}
}
看来您是在fragment_main.xml而不是activity_main.xml中建立视图的。
首次创建新的android项目时,您会拥有以下这些文件,这些文件会自动创建并打开:
然后,当您开始时,您可以在fragment_main.xml
文件中添加视图(例如:TextView) 。 而您尝试在Activity
使用此视图进行一个基本的事件,如下所示:
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); // Using layout activity_main.xml
// You try to set a simple text on the view (TextView) previously added
TextView text = (TextView) findViewById(R.id.textView1);
text.setText("Simple Text"); // And you get an error here!
/*
* You do an fragment transaction to add PlaceholderFragment Fragment
* on screen - this below snippnet is automatically created.
*/
if(savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
您无法运行您的应用程序,或者有时您只有白屏,因为您尝试调用/显示的视图布局错误。
解决方案: 将onCreateView方法中的所有内容移到Fragment类中。 调用视图并在相关片段而不是父活动中执行某些操作 。
例如,对于您的情况:
public static class PlaceholderFragment extends Fragment {
int counter;
Button add, sub;
TextView display;
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
counter = 0;
// Don't forget to attach your view to the inflated view as "rootView.findViewById()"
add = (Button) rootView.findViewById(R.id.bAdd);
sub = (Button) rootView.findViewById(R.id.bSub);
display = (TextView) rootView.findViewById(R.id.textDisp);
add.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Perform action on click
counter++;
}
});
return rootView;
}
}
我得到了解决方案,我也进行了测试
问题不只是将代码移入
但我在移动代码后也必须使用以下内容
add = (Button) rootView.findViewById (R.id.bAdd);
sub = (Button) rootView.findViewById(R.id.bSub);
display = (TextView) rootView.findViewById(R.id.tvDisplay);
代替以下
add = (Button) findViewById (R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.tvDisplay);
我希望任何机构在这里发表评论以解释这种行为
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