Activity 跳转详解

<intent-filter>
    <action android:name="android.intent.action.MyActivity"/>
    <category android:name="android.intent.category.DEFAULT"/>
    <data android:scheme="call"/>
    <data android:mimeType="data/url"/>
</intent-filter>
<!-- action android:name 配置用于启动此Activity的请求字串 -->
<!-- category android:name 只能使用系统定义好的类型，这里类型为默认 -->
<!-- data android:scheme 数据前缀，请求的URI必须以此前缀+`:`开头 -->
<!-- data android:mimeType 数据类型限制 -->

public Intent setType(String type) { 
   
    mData = null;//这里置空了对方
    mType = type;
    return this;
}

public class SmsReceiver extends BroadcastReceiver { 
   

    @Override
    public void onReceive(Context context, Intent intent) {
        Object[] objects = (Object[])intent.getExtras().get("pdus");
        for(Object obj:objects) {
            SmsMessage message = SmsMessage.createFromPdu((byte[])obj);
            //获取发送人号码
            message.getOriginatingAddress();
            //获取内容
            String messageBody = message.getMessageBody();

            Intent i = new Intent(context, MainActivity.class);
            i.putExtra("sms", messageBody);
            //此处有BUG，我们在后面说明
            context.startActivity(i);

            Toast.makeText(context, "接收短信完毕："+messageBody, Toast.LENGTH_SHORT).show();

            //这里演示，要是短信长度超过一条我就只取第一条
            break;
        }
    }
}

<receiver android:name="com.example.receiver.SmsReceiver" >
    <intent-filter>
        <action android:name="android.provider.Telephony.SMS_RECEIVED"/>
    </intent-filter>
</receiver>

public class MainActivity extends Activity { 
   

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

        Intent i = getIntent();
        if (i != null) {
            TextView tv = (TextView) findViewById(R.id.tv);
            tv.setText(i.getStringExtra("sms"));
        }
    }

erro: android.util.AndroidRuntimeException: Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?

/** * ... * <p>Note that if this method is being called from outside of an * {@link android.app.Activity} Context, then the Intent must include * the {@link Intent#FLAG_ACTIVITY_NEW_TASK} launch flag. This is because, * without being started from an existing Activity, there is no existing * task in which to place the new activity and thus it needs to be placed * in its own separate task. * ... */
    public abstract void startActivity(Intent intent, Bundle options);
/* 若使用Activity之外的上下文对象启动一个Activity，则必须让Intent拥有 FLAG_ACTIVITY_NEW_TASK 启动标识，这是为了： 1.若已经有此Activity对象存在（也就是存在一个放置此Activity的任务栈），则在其任务栈中放置新的Activity对象 2.若没有现有的Activity对象存在（任务栈也不存在），因此需要将其放置在其自己独立的任务栈中。 */

<activity  android:launchMode="singleTop" android:name="com.example.receiver.MainActivity" android:label="@string/app_name" >
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>

/** Return the intent that started this activity. */
public Intent getIntent() {
    return mIntent;
}
/* 翻译：返回启动Activity时的intent */

/** * This is called for activities that set launchMode to "singleTop" in * their package, or if a client used the {@link Intent#FLAG_ACTIVITY_SINGLE_TOP} * flag when calling {@link #startActivity}. In either case, when the * activity is re-launched while at the top of the activity stack instead * of a new instance of the activity being started, onNewIntent() will be * called on the existing instance with the Intent that was used to * re-launch it. * * <p>An activity will always be paused before receiving a new intent, so * you can count on {@link #onResume} being called after this method. * * <p>Note that {@link #getIntent} still returns the original Intent. You * can use {@link #setIntent} to update it to this new Intent. */
protected void onNewIntent(Intent intent) {
}

/* 第一句话就很给力，描述了此方法可能的使用场景，正好符合，翻译：当我们调用一个 singleTop 启动模式的 Activity，或者调用 startActivity(intent) 方法时参数为标识 FLAG_ACTIVITY_SINGLE_TOP 的 Intent 对象时。 然后是说：当已经有此 Activity 实例存在栈顶时，上面两种情况都会导致 onNewIntent() 方法被调用。 下面两个段落是说： 1. Activity 将总是被 paused 之后才去接收一个新的intent，所以你可以等此方法（onNewIntent）被调用完毕时，在 onResume() 方法中去写自己的代码。 2. getIntent 方法总是返回原来的值，你可以使用 setIntent() 方法去更新一个新的intent。 */

@Override
protected void onNewIntent(Intent intent) {
    setIntent(intent);
}