这是我第一次使用 recyclerview,我收到一些关于 android:onClick="addItem"
的错误 这是我尝试向我的 recyclerview 添加一行文本时得到的结果.我通常使用手机来测试我的应用。
java.lang.IllegalStateException: Could not execute method of the activity
at android.view.View$1.onClick(View.java:4012)
at android.view.View.performClick(View.java:4761)
at android.view.View$PerformClick.run(View.java:19767)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4007)
at android.view.View.performClick(View.java:4761)
at android.view.View$PerformClick.run(View.java:19767)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
at com.sapps.app.testapp2.MainActivity.addItem(MainActivity.java:53)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4007)
at android.view.View.performClick(View.java:4761)
at android.view.View$PerformClick.run(View.java:19767)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
这是我的代码,我认为是错误的地方,但我不完全知道:
public class MainActivity extends ActionBarActivity {
private EditText mText;
private RecyclerView.LayoutManager mLayoutManager;
private RecyclerView recyclerView;
private Button btn;
private CustomRecyclerAdapter mAdapter;
private List<Data> mData = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initializing views.
mText = (EditText) findViewById(R.id.textEt);
recyclerView = (RecyclerView) findViewById(R.id.recycler);
// If the size of views will not change as the data changes.
recyclerView.setHasFixedSize(true);
// Setting the LayoutManager.
mLayoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(mLayoutManager);
// Setting the adapter.
CustomRecyclerAdapter mAdapter = new CustomRecyclerAdapter();
recyclerView.setAdapter(mAdapter);
}
// Called when add button is clicked.
public void addItem(View v) {
if(mText!=null) {
Data dataToAdd = new Data(mText.getText().toString()); mData.add(dataToAdd);
}
}
这是我的 recyclerview 适配器,可以确定:
public class CustomRecyclerAdapter extends RecyclerView.Adapter<RecyclerViewHolder> {
CustomRecyclerAdapter mAdapter;
private List<Data> mData = Collections.emptyList();
public CustomRecyclerAdapter() {
// Pass context or other static stuff that will be needed.
}
public void updateList(List<Data> data) {
mData = data;
notifyDataSetChanged();
}
@Override
public int getItemCount() {
return mData.size();
}
@Override
public RecyclerViewHolder onCreateViewHolder(ViewGroup viewGroup, int position) {
LayoutInflater inflater = LayoutInflater.from(viewGroup.getContext());
View itemView = inflater.inflate(R.layout.list_item, viewGroup, false);
return new RecyclerViewHolder(itemView);
}
@Override
public void onBindViewHolder(RecyclerViewHolder viewHolder, int position) {
viewHolder.title.setText(mData.get(position).text);
}
public void addItemInRec(int position, Data data) {
mData.add(data);
notifyItemInserted(position);
}
public void removeItem(int position) {
mData.remove(position);
notifyItemRemoved(position);
}
}
我的 MainActivity xml 文件:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<EditText
android:id="@+id/textEt"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:hint="Text"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Add"
android:onClick="addItem"/>
</LinearLayout>
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical"/>
</LinearLayout>
也许是我的 ViewHolder:
public class RecyclerViewHolder extends RecyclerView.ViewHolder {
public TextView title;
public RecyclerViewHolder(View itemView) {
super(itemView);
title = (TextView) itemView.findViewById(R.id.title);
}
}
或者Data.java类:
public class Data {
public String text;
public Data(String text) {
this.text = text;
}
}
最佳答案
关键在你的错误信息中:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
at com.sapps.app.testapp2.MainActivity.addItem(MainActivity.java:53)
从错误输出中学习的一个好技巧是查看每个“由”声明,并扫描日志,直到找到引用了您自己的文件之一。然后错误日志的那部分甚至会告诉您代码在哪一行失败(在本例中是 MainActivity.java 的第 53 行)。
Java 中的空指针异常是指您尝试在某个对象“A”上调用方法,但该对象“A”当前为 null
。
所以这个错误信息意味着: “在 MainActivity.java 的第 53 行,你试图调用一些尚不存在的对象的方法,所以我崩溃了。”
失败的方法是 EditText mText = (EditText) findViewById(R.id.textEt);
通常这种类型的失败意味着您没有从布局中找到正确的 ID。仔细检查 textEt
是否是此布局元素的正确 ID。
编辑:
仍然不确定为什么您的 View 没有被填充,但我确实注意到您的适配器有错误。您正在重新定义 mAdapter
,因此您有 2 个副本,一个在本地范围内,另一个作为 MainActivity 的成员。这肯定会把事情搞砸。
就在这里:
// Setting the adapter.
CustomRecyclerAdapter mAdapter = new CustomRecyclerAdapter();
recyclerView.setAdapter(mAdapter)
您正在本地重新定义 mAdapter
。改为这样做:
// Setting the adapter.
mAdapter = new CustomRecyclerAdapter();
recyclerView.setAdapter(mAdapter)
关于java - android java onClick 无法执行 Activity 的方法,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29287152/