java天文钟模拟器
他是java新手,正在学习从头开始构建计时器应用程序的教程。 应用程序可以编译,但在emulator中按start或stop时,应用程序崩溃。 在没有通知的情况下启动应用程序, 暂停带有崩溃通知的崩溃应用程序并填写报告建议, 停止不崩溃,但什么也不做。 我已经搜索了很多关于它的网站,似乎没有发现任何问题
主要活动java
package com.example.dayswithout;
import 安卓x.appcompat.app.AppCompatActivity;
import 安卓.os.Bundle;
import 安卓.os.SystemClock;
import 安卓.view.View;
import 安卓.widget.Chronometer;
import 安卓.widget.Toast;
public class MainActivity extends AppCompatActivity {
private Chronometer chronometer;
private long pauseOffset;
private Boolean running;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
chronometer=findViewById(R.id.chronometer);
chronometer.setFormat("Time: %s");
chronometer.setBase(SystemClock.elapsedRealtime());
chronometer.setOnChronometerTickListener(new Chronometer.OnChronometerTickListener() {
@Override
public void onChronometerTick(Chronometer chronometer) {
if ((SystemClock.elapsedRealtime() - chronometer.getBase()) >= 10000) {
chronometer.setBase(SystemClock.elapsedRealtime());
Toast.makeText(MainActivity.this, "Bing!", Toast.LENGTH_SHORT).show();
}
}
});
}
public void startChronometer(View v){
if(!running) {
chronometer.setBase(SystemClock.elapsedRealtime()-pauseOffset);
chronometer.start();
running = true;
}
}
public void pauseChronometer(View v){
if(running) {
chronometer.stop();
pauseOffset=SystemClock.elapsedRealtime()-chronometer.getBase();
running = false;
}
}
public void resetChronometer(View v){
chronometer.setBase(SystemClock.elapsedRealtime());
pauseOffset=0;
}
}
活动主xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
xmlns:app="http://schemas.安卓.com/apk/res-auto"
xmlns:tools="http://schemas.安卓.com/tools"
安卓:layout_width="match_parent"
安卓:layout_height="match_parent"
安卓:orientation="vertical"
安卓:gravity="center"
tools:context=".MainActivity">
<Chronometer
安卓:id="@+id/chronometer"
安卓:layout_width="wrap_content"
安卓:layout_height="wrap_content"
安卓:textSize="30sp" />
<Button
安卓:layout_width="wrap_content"
安卓:layout_height="wrap_content"
安卓:onClick="startChronometer"
安卓:text="Start"/>
<Button
安卓:layout_width="wrap_content"
安卓:layout_height="wrap_content"
安卓:text="Pause"
安卓:onClick="pauseChronometer"/>
<Button
安卓:layout_width="wrap_content"
安卓:layout_height="wrap_content"
安卓:text="reset"
安卓:onClick="resetChronometer"/>
</LinearLayout>
日志
02/22 14:19:49: Launching 'app' on No Devices.
Install successfully finished in 1 s 718 ms.
$ adb shell am start -n "com.example.dayswithout/com.example.dayswithout.MainActivity" -a 安卓.intent.action.MAIN -c 安卓.intent.category.LAUNCHER
Connected to process 6915 on device 'emulator-5554'.
Capturing and displaying logcat messages from application. This behavior can be disabled in the "Logcat output" section of the "Debugger" settings page.
I/ple.dayswithou: Not late-enabling -Xcheck:jni (already on)
I/ple.dayswithou: Unquickening 12 vdex files!
W/ple.dayswithou: Unexpected CPU variant for X86 using defaults: x86
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
D/libEGL: loaded /vendor/lib/egl/libEGL_emulation.so
D/libEGL: loaded /vendor/lib/egl/libGLESv1_CM_emulation.so
D/libEGL: loaded /vendor/lib/egl/libGLESv2_emulation.so
W/ple.dayswithou: Accessing hidden method L安卓/view/View;->computeFitSystemWindows(L安卓/graphics/Rect;L安卓/graphics/Rect;)Z (greylist, reflection, allowed)
W/ple.dayswithou: Accessing hidden method L安卓/view/ViewGroup;->makeOptionalFitsSystemWindows()V (greylist, reflection, allowed)
D/HostConnection: HostConnection::get() New Host Connection established 0xebb41ac0, tid 7013
D/HostConnection: HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_async_frame_commands ANDROID_EMU_gles_max_version_2
W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
D/EGL_emulation: eglCreateContext: 0xebb41a50: maj 2 min 0 rcv 2
D/EGL_emulation: eglMakeCurrent: 0xebb41a50: ver 2 0 (tinfo 0xebe96950) (first time)
I/Gralloc4: mapper 4.x is not supported
D/HostConnection: createUnique: call
HostConnection::get() New Host Connection established 0xebb41eb0, tid 7013
D/goldfish-address-space: allocate: Ask for block of size 0x100
allocate: ioctl allocate returned offset 0x3fbda9000 size 0x2000
D/HostConnection: HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_async_frame_commands ANDROID_EMU_gles_max_version_2
I/OpenGLRenderer: Davey! duration=1037ms; Flags=1, IntendedVsync=748790555628, Vsync=748807222294, OldestInputEvent=9223372036854775807, NewestInputEvent=0, HandleInputStart=748815462000, AnimationStart=748815491400, PerformTraversalsStart=748816913000, DrawStart=749730608800, SyncQueued=749763725800, SyncStart=749765306700, IssueDrawCommandsStart=749765382800, SwapBuffers=749827691200, FrameCompleted=749829712000, DequeueBufferDuration=138600, QueueBufferDuration=791000, GpuCompleted=-2920196950870201425,
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.dayswithout, PID: 6915
java.lang.IllegalStateException: Could not execute method for 安卓:onClick
at 安卓x.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:414)
at 安卓.view.View.performClick(View.java:7448)
at com.google.安卓.material.button.MaterialButton.performClick(MaterialButton.java:1119)
at 安卓.view.View.performClickInternal(View.java:7425)
at 安卓.view.View.access$3600(View.java:810)
at 安卓.view.View$PerformClick.run(View.java:28305)
at 安卓.os.Handler.handleCallback(Handler.java:938)
at 安卓.os.Handler.dispatchMessage(Handler.java:99)
at 安卓.os.Looper.loop(Looper.java:223)
at 安卓.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.安卓.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at 安卓x.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409)
at 安卓.view.View.performClick(View.java:7448)
at com.google.安卓.material.button.MaterialButton.performClick(MaterialButton.java:1119)
at 安卓.view.View.performClickInternal(View.java:7425)
at 安卓.view.View.access$3600(View.java:810)
at 安卓.view.View$PerformClick.run(View.java:28305)
at 安卓.os.Handler.handleCallback(Handler.java:938)
at 安卓.os.Handler.dispatchMessage(Handler.java:99)
at 安卓.os.Looper.loop(Looper.java:223)
at 安卓.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.安卓.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference
at com.example.dayswithout.MainActivity.startChronometer(MainActivity.java:35)
at java.lang.reflect.Method.invoke(Native Method)
at 安卓x.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409)
at 安卓.view.View.performClick(View.java:7448)
at com.google.安卓.material.button.MaterialButton.performClick(MaterialButton.java:1119)
at 安卓.view.View.performClickInternal(View.java:7425)
at 安卓.view.View.access$3600(View.java:810)
at 安卓.view.View$PerformClick.run(View.java:28305)
at 安卓.os.Handler.handleCallback(Handler.java:938)
at 安卓.os.Handler.dispatchMessage(Handler.java:99)
at 安卓.os.Looper.loop(Looper.java:223)
at 安卓.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.安卓.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:947)
I/Process: Sending signal. PID: 6915 SIG: 9
# 1 楼答案
该错误表示您的对象未实例化:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference
Boolean
是一种Object
类型,一种引用类型,需要实例化。在您的例子中private Boolean running;
是声明的,但它从未被实例化,导致上面的NullPointerException
相反,将类型从
Boolean
更改为primitveboolean
。您没有来初始化它,因为它将使用默认值false
。然而,为了可读性,初始化它可能是明智的private boolean running = false;
# 2 楼答案
这里有一个问题:
这表示
running
变量未初始化:我建议将它从包装的
Boolean
更改为一个对象且未设置,因此它的值为null
。到声明中的基元boolean
:对于Clarity,可能将其设置为false(可选,因为false是默认值)