【Android新手求助】为什么创建新线程后App会闪退

[Keyon同学]

本人大二Android新手，在做课本例题时遇到了很多闪退的问题，原因各种各样，现在又遇到了加入开启线程的代码后程序崩溃的问题，请大佬给予指点


还有一个问题就是 烦请大佬解释下extends AppCompatActivity和extends Activity的区别，因为书上的例题代码用的编译软件是Eclipse，所有MainActivity都是继承自Activity的，而我用的是Android Studio，默认是继承自AppCompatActivity的，有时候程序闪退就是继承的原因，有时候需要继承Activity才能运行，而有时候要继承AppCompatActivity才能用，能麻烦解释一下吗


标题所讲的问题代码（一个产生随机数的程序）如下所示：

public class MainActivity extends AppCompatActivity implements Runnable {
    private TextView tv_random;
    private Handler handler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv_random = (TextView) findViewById(R.id.random);

        Thread t = new Thread(this);
        t.start();

        handler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                if (msg.what == 0x101) {
                    tv_random.setText(msg.obj.toString());
                }
                super.handleMessage(msg);
            }
        };
    }

    @Override
    public void run() {
        String value = "";
        int max = 9999999;
        int min = 1000000;
        while (!Thread.currentThread().isInterrupted()){
            value = String.valueOf(new Random().nextInt(max)%(max-min+1)+min);
            Message m = handler.obtainMessage();
            m.obj = value;
            m.what = 0x101;
            handler.sendMessage(m);
            try {
                Thread.sleep(1000);
            }catch (InterruptedException e){
                e.printStackTrace();
            }
        }
    }
}

[x443137254]

楼上说的可能是对的，或者你把睡1秒那句话往上拉，先睡1秒再发消息，就保证没问题，还有一种写法是在声明成员变量的时候就直接初始化，这个能保证是第一时间得到初始化

[r00_a2lBUR]

Message m = handler.obtainMessage(); 换成new的方式可能就不闪退了

[Shay24156]

AppcompaActivity相对于Activity的主要的两点变化； 1：主界面带有toolbar的标题栏； 2，theme主题只能用android:theme=”@style/AppTheme （appTheme主题或者其子类），而不能用android:style。 否则会提示错误： Caused by: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity. 至于具体为什么报错.建议你把log信息附上

[Keyon同学]

引用 1 楼 r00_a2lBUR 的回复:

Message m = handler.obtainMessage(); 换成new的方式可能就不闪退了

用new的方式写还是不行…

[Keyon同学]

再运行一次莫名其妙的好了，但是我还是给log贴出来请大神帮忙解读下哪里有问题吧 刚学不怎么会看log信息

$ adb shell am start -n "com.example.exam7_1/com.example.exam7_1.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Client not ready yet..Waiting for process to come online
Connected to process 16420 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.
W/zygote: JIT profile information will not be recorded: profile file does not exits.
I/chatty: uid=10106(com.example.exam7_1) identical 10 lines
W/zygote: JIT profile information will not be recorded: profile file does not exits.
I/MemoryIntArray: created from parcel MemoryIntArray@24256559 mMemoryAddr=3955920896 mFd=47
I/InstantRun: starting instant run server: is main process
I/zygote: Background concurrent copying GC freed 10573(2MB) AllocSpace objects, 0(0B) LOS objects, 57% free, 1135KB/2MB, paused 7.349ms total 82.076ms
W/zygote: Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (light greylist, reflection)
          Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (light greylist, reflection)
D/OpenGLRenderer: HWUI GL Pipeline
D/: HostConnection::get() New Host Connection established 0xe189e240, tid 16452
I/ConfigStore: android::hardware::configstore::V1_0::ISurfaceFlingerConfigs::hasWideColorDisplay retrieved: 0
I/ConfigStore: android::hardware::configstore::V1_0::ISurfaceFlingerConfigs::hasHDRDisplay retrieved: 0
I/OpenGLRenderer: Initialized EGL, version 1.4
D/OpenGLRenderer: Swap behavior 1
W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
D/OpenGLRenderer: Swap behavior 0
D/EGL_emulation: eglCreateContext: 0xe3549380: maj 2 min 0 rcv 2
D/EGL_emulation: eglMakeCurrent: 0xe3549380: ver 2 0 (tinfo 0xe967ee50)
D/EGL_emulation: eglMakeCurrent: 0xe3549380: ver 2 0 (tinfo 0xe967ee50)

[江三木洛]

Thread t = new Thread(this); t.start(); handler = new Handler() { @Override public void handleMessage(Message msg) { if (msg.what == 0x101) { tv_random.setText(msg.obj.toString()); } super.handleMessage(msg); } }; 应该是空指针，在新线程里handler.sendMessage(m);时不能保证handler已经被初始化了，把handler = new Handler()放在start前面