第一个Android应用程序崩溃,但代码中没有错误
这是我在emulator上运行应用程序时的日志,我是应用程序开发新手,有人能帮我吗?如果需要的话,我会发布代码,但是它被分为多个活动第一个Android应用程序崩溃,但代码中没有错误,android,Android,这是我在emulator上运行应用程序时的日志,我是应用程序开发新手,有人能帮我吗?如果需要的话,我会发布代码,但是它被分为多个活动 10-17 08:45:43.269 2696-2696/? I/art﹕ Not late-enabling -Xcheck:jni (already on) 10-17 08:45:43.269 2696-2696/? I/art﹕ Late-enabling JIT 10-17 08:45:43.273 2696-2696/? I/art﹕
10-17 08:45:43.269 2696-2696/? I/art﹕ Not late-enabling -Xcheck:jni (already on)
10-17 08:45:43.269 2696-2696/? I/art﹕ Late-enabling JIT
10-17 08:45:43.273 2696-2696/? I/art﹕ JIT created with code_cache_capacity=2MB compile_threshold=1000
10-17 08:45:43.304 2696-2696/? W/System﹕ ClassLoader referenced unknown path: /data/app/com.victorioussecrets.nwureferencegenerator-2/lib/x86
10-17 08:45:43.427 2696-2696/com.victorioussecrets.nwureferencegenerator D/AndroidRuntime﹕ Shutting down VM
10-17 08:45:43.427 2696-2696/com.victorioussecrets.nwureferencegenerator E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.victorioussecrets.nwureferencegenerator, PID: 2696
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.victorioussecrets.nwureferencegenerator/com.victorioussecrets.nwureferencegenerator.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.victorioussecrets.nwureferencegenerator.MainActivity.onCreate(MainActivity.java:31)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
10-17 08:45:47.140 2696-2696/? I/Process﹕ Sending signal. PID: 2696 SIG: 9
我已经修复了空错误,现在是以后的新日志
10-17 09:28:23.871 3195-3195/com.victorioussecrets.nwureferencegenerator E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.victorioussecrets.nwureferencegenerator, PID: 3195
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.widget.Spinner.getSelectedItem()' on a null object reference
at com.victorioussecrets.nwureferencegenerator.MainActivity.onItemSelected(MainActivity.java:70)
at android.widget.AdapterView.fireOnSelected(AdapterView.java:922)
at android.widget.AdapterView.dispatchOnItemSelected(AdapterView.java:911)
at android.widget.AdapterView.-wrap1(AdapterView.java)
at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:881)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
这是我的MainActivity.java
package com.victorioussecrets.nwureferencegenerator;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {
Spinner spinnerStyles;
Button btnExit;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnExit = (Button)findViewById(R.id.btnExit);
Spinner spinner = (Spinner)findViewById(R.id.spinnerStyles);
ArrayAdapter adapter = ArrayAdapter.createFromResource(this,R.array.arrStyles,android.R.layout.simple_spinner_item);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener(this);
btnExit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
finish();
System.exit(0);
}
});
}
@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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String spinVal = "";
spinVal = spinnerStyles.getSelectedItem().toString();
if(spinVal.equals("NWU Harvard")) {
startActivity(new Intent(MainActivity.this, nwu_harvard.class));
}
if(spinVal.equals("LAW")) {
startActivity(new Intent(MainActivity.this, law.class));
}
if(spinVal.equals("APA")) {
startActivity(new Intent(MainActivity.this, apa.class));
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
}
这是西北大学哈佛大学的第一次图书活动
包com.victorioussecrets.nUreferenceGenerator
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class nwu_harvard_book extends AppCompatActivity {
Button btnBack,btnGenerate;
String stringf= "",value1= "",value3= "",value2= "",value4= "",value5= "";
EditText inputTxt = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.nwu_harvard_book);
btnGenerate = (Button) findViewById(R.id.btngenerate);
btnBack = (Button) findViewById(R.id.btnBack);
btnBack.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
finish();
}
});
btnGenerate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
inputTxt = (EditText) findViewById(R.id.edtAuthor);
value1 = inputTxt.getText().toString();
inputTxt = (EditText) findViewById(R.id.edtTitle);
value2 = inputTxt.getText().toString();
inputTxt = (EditText) findViewById(R.id.edtDate);
value3 = inputTxt.getText().toString();
inputTxt = (EditText) findViewById(R.id.edtEdition);
value4 = inputTxt.getText().toString();
inputTxt = (EditText) findViewById(R.id.edtTown);
value5 = inputTxt.getText().toString();
stringf = (value1+". "+value3+". "+value2+". "+value4+". "+value5+".");
Intent intent = new Intent(nwu_harvard_book.this, output.class);
intent.putExtra("output", stringf);
startActivity(intent);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.nwu_harvard_book, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
这是第二次nwu哈佛大学文章活动
package com.victorioussecrets.nwureferencegenerator;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class nwu_harvard_article extends AppCompatActivity {
Button btnBack,btnGenerate;
String stringf= "",value1= "",value3= "",value2= "",value4= "",value5= "",value6= "";
EditText inputTxt = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.nwu_harvard_book);
btnGenerate = (Button) findViewById(R.id.btngenerate);
btnBack = (Button) findViewById(R.id.btnBack);
btnBack.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
finish();
}
});
btnGenerate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
inputTxt = (EditText) findViewById(R.id.edtAuthor);
value1 = inputTxt.getText().toString();
inputTxt = (EditText) findViewById(R.id.edtTitle);
value2 = inputTxt.getText().toString();
inputTxt = (EditText) findViewById(R.id.edtDate);
value3 = inputTxt.getText().toString();
inputTxt = (EditText) findViewById(R.id.edtpages);
value4 = inputTxt.getText().toString();
inputTxt = (EditText) findViewById(R.id.edtmagtitle);
value5 = inputTxt.getText().toString();
inputTxt = (EditText) findViewById(R.id.edtVolume);
value6 = inputTxt.getText().toString();
stringf = (value1+". "+value3+". "+value2+" "+value5+". "+value6+".");
Intent intent = new Intent(nwu_harvard_article.this, output.class);
intent.putExtra("output", stringf);
startActivity(intent);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.nwu_harvard_book, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
你的按钮是空的。您必须初始化它
Button button = (Button)findViewById(R.id.your_id);
或
您的onCreate活动方法存在问题。检查xml按钮id是否与onCreate相同
Button button = (Button)findViewById(R.id.button1);
在所有3个场景中,您都得到了NPE(NullPointerException)。
第一种情况-带有按钮视图的NPE未在MainActivity中初始化: 我认为行是
btnExit.setOnClickListener(
)。您使用Hossein Gerami提供的解决方案解决了这个问题,并可能添加了btnExit=(按钮)findViewById(R.id.btnExit);
第二种情况-未在MainActivity中初始化微调器的NPE选定方法:这里的行是spinVal=spinnerStyles.getSelectedItem().toString();
您在初始化喷丝头样式或使用其他替代方法后修复了它
第三种情况-在nwu\U harvard\U文章中,带EditText的NPE为空:在这种情况下,正如Logcat报告中指出的那样
java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
at com.victorioussecrets.nwureferencegenerator.nwu_harvard_article$2.onClick(nwu_harvard_article.java:43)
在这种情况下,行是value4=inputText.getText().toString();
现在为什么这里inputText为空呢?行上方的代码使inputText为空,这是inputText=(EditText)findViewById(R.id.edtpages);
这意味着版面没有id为R.id.edtpages的EditText。在活动
nwu_哈佛_文章
和nwu_哈佛_书籍
中,您分配的布局相同,即setContentView(R.layout.nwu_哈佛_书籍)
因此请输入所有EditText视图的id。我确信您的EditText具有idedtAuthor、edtTitle和edtDate
。这就是为什么在出现问题后,您在nwu哈佛大学的文章中直到值3才获得NPE的原因。因此请正确检查布局
建议说明:请确切了解NPE的来源。您呢 可以很容易地修复它,因为在logcat报告中,您可以清楚地看到给出此NPE并导致应用程序崩溃的行。
例如: 在上面的一行中,您可以看到nwu_harvard_article.java:43。这是一个超链接行,意味着您可以单击它,如果您单击它,它将直接带您到文件中的行,该行在您的情况下抛出错误,它将是值4…同时第一行指定您获得NPE的原因
在
ActivityThread.java
的第2416行,您有一个null
对象。您试图在一个为null的按钮上设置setOnClickListener,只需在onCeate(findViewById)中定义您的按钮。发布主活动现在您在不同的行获得NPE…无论如何,spinVal=spinnerStyles.getSelectedItem().toString();您在哪里初始化了spinnerStyles?感谢您的帮助我非常感谢您和@ShadowDroid我还有最后一个错误很抱歉编码不好我现在就编辑并添加它
Button button = (Button)findViewById(R.id.button1);
java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
at com.victorioussecrets.nwureferencegenerator.nwu_harvard_article$2.onClick(nwu_harvard_article.java:43)
java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
at com.victorioussecrets.nwureferencegenerator.nwu_harvard_article$2.onClick(nwu_harvard_article.java:43)