Android 我想调用getView覆盖方法中的mainActivity…..它显示致命异常..如何解决它
mainActivity.javaAndroid 我想调用getView覆盖方法中的mainActivity…..它显示致命异常..如何解决它,android,nullpointerexception,Android,Nullpointerexception,mainActivity.java public class MainActivity extends AppCompatActivity { ListView listView; ListViewAdaptor adapter; TextView txtname1,txtrank1; RelativeLayout relativeLayout; Context context; ArrayList<String> name;
public class MainActivity extends AppCompatActivity {
ListView listView;
ListViewAdaptor adapter;
TextView txtname1,txtrank1;
RelativeLayout relativeLayout;
Context context;
ArrayList<String> name;
ArrayList<Integer> rank;
int highestRank = 39;
public MainActivity() {
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = findViewById(R.id.listview);
relativeLayout = (RelativeLayout) findViewById(R.id.rlFloter);
txtname1 = findViewById(R.id.txtName);
txtrank1 = findViewById(R.id.txtRank);
name = new ArrayList<>();
rank = new ArrayList<>();
for(int i=1 ; i<40 ; i++){
name.add("Winit Employer"+i);
rank.add(i); }
txtname1.setText("Winit Employer39");
txtrank1.setText("39");
adapter = new ListViewAdaptor(this,name,rank);
listView.setAdapter(adapter);
}
public void visible() {
txtname1.setVisibility(View.VISIBLE);
txtrank1.setVisibility(View.VISIBLE);
}
public void gone() {
txtname1.setVisibility(View.GONE);
txtrank1.setVisibility(View.GONE);
}
public void toast() {
Toast.makeText(context,"Toast",Toast.LENGTH_LONG).show();
}
/////////////
public类MainActivity扩展了AppCompatActivity{
列表视图列表视图;
ListViewAdapter适配器;
TextView txtname1,txtrank1;
相对的相对的;
语境;
ArrayList名称;
ArrayList秩;
int-highestRank=39;
公共活动(){
}
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView=findViewById(R.id.listView);
relativeLayout=(relativeLayout)findViewById(R.id.rlFloter);
txtname1=findviewbyd(R.id.txtName);
txtrank1=findViewById(R.id.txtRank);
name=新的ArrayList();
秩=新的ArrayList();
for(int i=1;i变量上下文未初始化
删除变量并在activity toast方法中使用this
Toast.makeText(this,"Toast",Toast.LENGTH_LONG).show();
变量上下文
未初始化
删除变量并在activity toast方法中使用this
Toast.makeText(this,"Toast",Toast.LENGTH_LONG).show();
有两种解决方案,一种是@SamuelRobert建议的,另一种是add
context = MainActivity.this
在MainActivity的onCreate方法中。有两种解决方案,一种是@SamuelRobert建议的,另一种是add
context = MainActivity.this
在MainActivity的onCreate方法中。上下文变量是冗余的。因为这个
更好地传达了活动中的上下文。而且代码更少!这总是好的上下文变量是冗余的。因为这个
更好地传达了活动中的上下文。代码更少!这总是好的