当我点击添加按钮而不是打开学生详细信息时，它表示应用程序已停止工作。 请帮我。 谢谢。
这是我的代码：
package com.example.rahul.myapplication;
import android.app.ListActivity;
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.os.Build;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.HashMap;
public class MainActivity extends ListActivity implements android.view.View.OnClickListener{
Button btnAdd,btnGetAll;
TextView student_Id;
@Override
public void onClick(View view) {
if (view== findViewById(R.id.btnAdd)){
Intent intent;
intent = new Intent(this,StudentDetail.class);
intent.putExtra("student_Id",0);
startActivity(intent);
}else {
StudentRepo repo = new StudentRepo(this);
ArrayList<HashMap<String, String>> studentList = repo.getStudentList();
if(studentList.size()!=0) {
ListView lv = getListView();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
student_Id = (TextView) view.findViewById(R.id.student_Id);
String studentId = student_Id.getText().toString();
Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
objIndent.putExtra("student_Id", Integer.parseInt( studentId));
startActivity(objIndent);
}
});
ListAdapter adapter = new SimpleAdapter( MainActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
setListAdapter(adapter);
}else{
Toast.makeText(this,"No student!",Toast.LENGTH_SHORT).show();
}
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnAdd = (Button) findViewById(R.id.btnAdd);
btnAdd.setOnClickListener(this);
btnGetAll = (Button) findViewById(R.id.btnGetAll);
btnGetAll.setOnClickListener(this);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.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);
}
}
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:fitsSystemWindows="true"
tools:context=".MainActivity">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Add"
android:id="@+id/btnAdd"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@android:id/list"
android:layout_centerHorizontal="true"
android:layout_alignParentTop="true"
android:layout_above="@+id/btnAdd" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="List All"
android:id="@+id/btnGetAll"
android:layout_alignParentBottom="true"
android:layout_toRightOf="@+id/btnAdd" />
<android.support.design.widget.AppBarLayout android:layout_height="wrap_content"
android:layout_width="match_parent" android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar android:id="@+id/toolbar"
android:layout_width="match_parent" android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary" app:popupTheme="@style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
<android.support.design.widget.FloatingActionButton android:id="@+id/fab"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:layout_gravity="bottom|end" android:layout_margin="@dimen/fab_margin"
android:src="@android:drawable/ic_dialog_email" />
</RelativeLayout>
当我点击添加按钮而不是打开学生详细信息时，它表示应用程序已停止工作。 请帮我。 谢谢。 Logcat显示
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: Process: com.example.rahul.myapplication, PID: 15064
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.rahul.myapplication/com.example.rahul.myapplication.StudentDetail}; have you declared this activity in your AndroidManifest.xml?
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1794)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.app.Instrumentation.execStartActivity(Instrumentation.java:1512)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.app.Activity.startActivityForResult(Activity.java:3917)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.app.Activity.startActivityForResult(Activity.java:3877)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.app.Activity.startActivity(Activity.java:4200)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.app.Activity.startActivity(Activity.java:4168)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at com.example.rahul.myapplication.MainActivity.onClick(MainActivity.java:52)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.view.View.performClick(View.java:5198)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.view.View$PerformClick.run(View.java:21147)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.os.Handler.handleCallback(Handler.java:739)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:95)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.os.Looper.loop(Looper.java:148)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5417)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
10-16 13:51:51.310 15064-15064/com.example.rahul.myapplication E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
答案 0 :(得分：0)
从
更改您的代码部分 @Override
public void onClick(View view) {
if (view== findViewById(R.id.btnAdd)){
Intent intent;
intent = new Intent(this,StudentDetail.class);
到
@Override
public void onClick(View view) {
if (view.getId() == R.id.btnAdd){
Intent intent;
intent = new Intent(MainActivity.this,StudentDetail.class);
View是一个类，你不使用==来比较两个实例 类而不是等于方法。
因此你的条件进入了else部分...因为它可能会抛出一些错误，因为根据你的逻辑，else部分的操作可能没有准备好。因为你的添加点击事件应该只在部分执行，而不是如上所述，所以进行更改并检查