小编Rah*_*han的帖子

这是我的布局：

...
<android.support.constraint.ConstraintLayout   
android:layout_width="0dp"
android:layout_height="match_parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintWidth_percent="0.6"
>
            <android.support.constraint.ConstraintLayout
                android:id="@+id/myclayout"
                android:layout_width="match_parent"
                android:layout_height="0dp"
                app:layout_constraintHeight_percent="0.2"
                app:layout_constraintTop_toTopOf="parent"
                ></android.support.constraint.ConstraintLayout>


 </android.support.constraint.ConstraintLayout>
...

如何以编程方式设置constraintHeight_percent？

我尝试使用 ConstraintSet 但没有用

ConstraintSet set = new ConstraintSet();
set.constrainPercentHeight(R.id.myclayout, (float) 0.4);
set.applyTo(((ConstraintLayout) vw.findViewById(R.id.myclayout)));

我能够发送带有单个附件的电子邮件，但我找不到在单个邮件中发送多个附件的任何内容

        try {
            SendGrid sendgrid = new SendGrid(SENDGRID_USERNAME, SENDGRID_PASSWORD);

            SendGrid.Email email = new SendGrid.Email();

            // Get values from edit text to compose email
            // TODO: Validate edit texts
            email.addTo(mTo);
            email.setFrom(mFrom);
            email.setSubject(mSubject);
            email.setText(mText);

            // Attach image
            if (mUri != null) {
                email.addAttachment(mAttachmentName, mAppContext.getContentResolver().openInputStream(mUri));
            }

            // Send email, execute http request
            SendGrid.Response response = sendgrid.send(email);
            mMsgResponse = response.getMessage();

            Log.d("SendAppExample", mMsgResponse);

        } catch (SendGridException | IOException e) {
            Log.e("SendAppExample", e.toString());
        }

        return null;
    }

我正在处理需要在后台服务中连续获取位置更新的应用程序.我使用了它正在使用的后台粘性服务.但是,即使我已经添加了启动广播并在那里启动了服务,服务也不会在启动完成后启动.服务开始并立即被杀死.

此外,这不适用于奥利奥.应用程序关闭几分钟后服务停止,直到应用程序重新启动后才会重新启动.

我已经浏览了很多链接,博客建议使用AlarmManager/JobScheduler/JobIntentService,但没有得到满意的解决方案.因此,请建议即使在启动后也可用于在后台持续获取位置的工作策略/解决方案,并且应该在Oreo上工作.

所以，我想制作一个在后台带有视频的应用程序，每当应用程序启动时，视频就会播放，但一个问题是它只播放一次并且从不循环。这是我的代码

 @Override
    protected void onResume() {
    super.onResume();
    VideoView video = (VideoView) findViewById(R.id.videoview1);
    Uri videoPath = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.great);
    video.setVideoURI(videoPath);
    video.start();
    }

当我使用setOnNavigationItemSelectedListener冻结BottomNavigationView波纹效果时，如下面的屏幕截图所示。并且效果状态一直保持这样。

我不明白为什么？

我在用着com.android.support:design:27.1.1

binding = DataBindingUtil
        .setContentView(this, R.layout.activity_main)

bottomBar = binding?.bottomBarNavigation as BottomNavigationView
bottomBar?.setOnNavigationItemSelectedListener {
    when (it.itemId) {
        TabBarObject.TAB_MESSENGER -> replaceFragment(
            MessengerFragment(),
            TabBarObject.TAB_MESSENGER.tabName
        )
        ...
        ...
    }
}

private fun getTabInfo(menuItemId: Int): TabBarObject {
    return when (menuItemId) {
        R.id.tab_messenger -> TabBarObject.TAB_MESSENGER
        ...
        ...
        else -> throw IllegalArgumentException("UNKNOWN TAB BAR TYPE")
    }
}

private fun replaceFragment(fragment: Fragment, tag: String): Boolean {
    val ft = supportFragmentManager.beginTransaction()

    ft.replace(R.id.frame_layout, fragment, tag)
    ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE)
    ft.commitAllowingStateLoss()
    return true
}

活动主文件

<?xml version="1.0" …

你好我有TextView的问题.这是我的代码

final TextView username = (TextView) _v.findViewById(R.id.username);
final LinearLayout linear7 = (LinearLayout) _v.findViewById(R.id.linear7);
final TextView date = (TextView) _v.findViewById(R.id.date);
final TextView msg = (TextView) _v.findViewById(R.id.msg);
final TextView username2 = (TextView) _v.findViewById(R.id.username);
final LinearLayout linear72 = (LinearLayout) _v.findViewById(R.id.linear7);
final TextView date2 = (TextView) _v.findViewById(R.id.date);
final TextView msg2 = (TextView) _v.findViewById(R.id.msg);
final LinearLayout linear999 = (LinearLayout) _v.findViewById(R.id.linear999);
final LinearLayout linear9992 = (LinearLayout) _v.findViewById(R.id.linear9992);

username.setText(map1.get((int)_position).get("name").toString());
msg.setText(map1.get((int)_position).get("msg").toString());
date.setText(map1.get((int)_position).get("date").toString());
username2.setText(username.getText().toString());
msg2.setText(msg.getText().toString());
date2.setText(date.getText().toString());

如您所见,username2应与用户名具有相同的文本.但是,它只有我在设计师中为它提供的文本.请帮忙.