Android 使用新线程时出现异常

Question

大家好，我正在尝试制作一个应用程序，通过 Toast 消息实时获取我的电池状态。所以，如果我插入电池充电器，它应该显示 "battery is charging"，如果我拔下充电器，它应该显示 "battery is discharging"，等等...为此我使用了一个新线程，但在运行时我的应用程序崩溃我在 logcat

中收到错误

这是我的代码和logcat：

public class MainActivity extends Activity {

Context cxt;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    bn = (Button) findViewById(R.id.button);
    cxt = this;


    Runnable myRunnable = new Runnable() {

        @Override
        public void run() {
            IntentFilter IF = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
            Intent BatteryStatus = cxt.registerReceiver(null, IF);
            int status = BatteryStatus.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
            boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING;
            boolean disCharging = status == BatteryManager.BATTERY_STATUS_DISCHARGING;
            boolean usbCharge = status == BatteryManager.BATTERY_PLUGGED_USB;
            boolean acCharging = status == BatteryManager.BATTERY_PLUGGED_AC;

            if (isCharging) {
                Toast.makeText(getBaseContext(), "La batteria è in carica", Toast.LENGTH_SHORT).show();
            }
            if (disCharging) {
                Toast.makeText(getBaseContext(), "La batteria è in scarica", Toast.LENGTH_SHORT).show();
            }
            if (usbCharge) {
                Toast.makeText(getBaseContext(), "La batteria è in carica tramite USB", Toast.LENGTH_SHORT).show();
            }
            if (acCharging) {
                Toast.makeText(getBaseContext(), "La batteria è in carica tramite AC", Toast.LENGTH_SHORT).show();
            }
        }
    };

    Thread myThread = new Thread(myRunnable);
    myThread.start();

}

这是我在 logcat 中遇到的错误：

01-04 11:10:10.696    7706-7723/com.example.matteo.battery E/AndroidRuntime﹕ FATAL EXCEPTION: Thread-4343
Process: com.example.matteo.battery, PID: 7706
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
        at android.os.Handler.<init>(Handler.java:200)
        at android.os.Handler.<init>(Handler.java:114)
        at android.widget.Toast$TN.<init>(Toast.java:336)
        at android.widget.Toast.<init>(Toast.java:100)
        at android.widget.Toast.makeText(Toast.java:250)
        at com.example.matteo.battery.MainActivity.run(MainActivity.java:43)
        at java.lang.Thread.run(Thread.java:818)

我想我在尝试启动新线程时出错了。

谢谢大家！

Answer 1

您无法在非 UI 主题中更新您的 UI，

您在 Toast 消息中收到错误，

如果你想在新线程中做一些代码并在更新 UI 之后你可以使用 AsyncTask，有关在新线程中更新 ui 的更多信息你可以看到 Update UI from Thread or see Documentation

Answer 2

您尝试实现的结果可以使用广播接收器更轻松地完成。查看 android 开发者网站的以下 official Documentation。

Answer 3

试试这个

if (isCharging) {
    MainActivity.this.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(MainActivity.this, "La batteria è in carica", Toast.LENGTH_SHORT).show();
                }
            });
}

应用于所有 Toast

不使用线程。创建一个 BroadcastReceiver

BroadcastReceiver receiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                int status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
                boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING;
                boolean disCharging = status == BatteryManager.BATTERY_STATUS_DISCHARGING;
                boolean usbCharge = status == BatteryManager.BATTERY_PLUGGED_USB;
                boolean acCharging = status == BatteryManager.BATTERY_PLUGGED_AC;
                //your code

            }
        };
        IntentFilter IF = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
        registerReceiver(receiver, IF);

或

BroadcastReceiver receiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                Thread myThread = new Thread(myRunnable);
myThread.start();

            }
        };
        IntentFilter IF = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
        registerReceiver(receiver, IF);

Answer 4

使用 runOnUiThread 在 UI 线程上运行指定的操作。

public class MainActivity extends Activity {

Context cxt;
Button bn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        bn = (Button) findViewById(R.id.button);
        cxt = this;


        Runnable myRunnable = new Runnable() {

            @Override
            public void run() {
                IntentFilter IF = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
                Intent BatteryStatus = cxt.registerReceiver(null, IF);
                int status = BatteryStatus.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
                boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING;
                boolean disCharging = status == BatteryManager.BATTERY_STATUS_DISCHARGING;
                boolean usbCharge = status == BatteryManager.BATTERY_PLUGGED_USB;
                boolean acCharging = status == BatteryManager.BATTERY_PLUGGED_AC;

                if (isCharging) {
                    showMessage("La batteria è in carica");
                }
                if (disCharging) {
                    showMessage("La batteria è in scarica");
                }
                if (usbCharge) {
                    showMessage("La batteria è in carica tramite USB");
                }
                if (acCharging) {
                    showMessage("La batteria è in carica tramite AC");
                }
            }
        };

        Thread myThread = new Thread(myRunnable);
        myThread.start();

    }

    private void showMessage(final String msg) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                Toast.makeText(getBaseContext(), msg, Toast.LENGTH_SHORT).show();
            }
        });
    }
}

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