小编N J*_*N J的帖子

我正在尝试显示循环视图时遇到异常:

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.support.v7.widget.RecyclerView$LayoutManager.canScrollVertically()' on a null object reference
at android.support.v7.widget.RecyclerView.computeVerticalScrollRange(RecyclerView.java:1216)
    at android.view.View.onDrawScrollBars(View.java:13900)
    at android.view.View.draw(View.java:16275)
    at android.support.v7.widget.RecyclerView.draw(RecyclerView.java:2440)
    at android.view.View.updateDisplayListIfDirty(View.java:15192)
    at android.view.View.getDisplayList(View.java:15215)
    at android.view.View.draw(View.java:15990)
    at android.view.ViewGroup.drawChild(ViewGroup.java:3708)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3502)
    at android.view.View.draw(View.java:16272)
    at android.view.View.updateDisplayListIfDirty(View.java:15192)
    at android.view.View.getDisplayList(View.java:15215)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3692)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3671)
    at android.view.View.updateDisplayListIfDirty(View.java:15152)
    at android.view.View.getDisplayList(View.java:15215)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3692)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3671)
    at android.view.View.updateDisplayListIfDirty(View.java:15152)
    at android.view.View.getDisplayList(View.java:15215)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:362)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3671)
    at android.view.View.updateDisplayListIfDirty(View.java:15152)
    at android.view.View.getDisplayList(View.java:15215)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3692)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3671)
    at android.view.View.updateDisplayListIfDirty(View.java:15152)
    at android.view.View.getDisplayList(View.java:15215)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3692)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3671)
    at android.view.View.updateDisplayListIfDirty(View.java:15152)
    at android.view.View.getDisplayList(View.java:15215)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3692) …

我有VisitingCardPOJO表格.我想要更新单个条目,如果 没有= 3

VisitingCardPOJO.java

public class VisitingCardPOJO extends RealmObject {

   @PrimaryKey private int no;
    private String name;
    private String address;

    public int getNo() {
        return no;
    }

    public void setNo(int no) {
        this.no = no;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

我有一个问题.我想用Button打开一个Activity但它一直崩溃.所以我创建了2个Classes和一个Button.但它一直在崩溃.

1. 类是activity_home class(),第二个是schedule_act()类.

activity_home类:

    package my.action.bat;

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;

    public class activity_home extends Activity {

        private Button ScheduleBtn;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            // TODO Auto-generated method stub
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);

             ScheduleBtn = (Button) findViewById(R.id.home_btn_schedule);

            ScheduleBtn.setOnClickListener(new View.OnClickListener() {

                public void onClick(View v) {
                    // TODO Auto-generated method stub


                    Intent myIntent = new Intent("my.action.bat.schedule_act");
                    startActivity(myIntent);


                }
            });
        }





    }  

schedule_act类:

package my.action.bat;

    import android.app.Activity;
    import android.os.Bundle;

    public class schedule_act extends Activity {

        @Override
        protected …

我ImageView在Android项目中使用了一个.

宽度:match_parent 高度:wrap_content

我将它缩放到了fill_XY,但图像还不是正方形......我该怎么办？

我试图创建一个ripple背景drawable为Button一个行程.

这是我到目前为止:

<ripple xmlns:android="http://schemas.android.com/apk/res/android"
    android:color="#336699">

    <item>
        <shape android:shape="rectangle">

            <solid android:color="#998811" />

            <stroke
                android:width="2dp"
                android:color="#119988" />

        </shape>
    </item>
</ripple>

但是通过这种解决方案,波纹与我的中风重叠.
我只想要ripple中风,我该怎么做？

我有以下代码:

public class MainActivity extends ListActivity { 
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}   
protected void onListItemClick(ListView l, View v, final int position, long id) {
    super.onListItemClick(l, v, position, id);
}}

我需要将其更改为onListItemLongClick()但是如何？可能吗？

这是我的代码Activity.启动一个Intent,然后一个Connection,对吧？

hello_service = new Intent(this, HelloService.class);
hello_service_conn = new HelloServiceConnection();
bindService( hello_service, hello_service_conn, Context.BIND_AUTO_CREATE);

但我的问题是......连接内部是什么？

   class HelloServiceConnection implements ServiceConnection {
        public void onServiceConnected(ComponentName className,IBinder boundService ) {

        }
        public void onServiceDisconnected(ComponentName className) {

        }
    };

有人能告诉我在ServiceConnected和onServiceDisconnected上添加了哪些代码？

我只想要一个基本的连接,以便我Activity和Service他人可以互相交谈.

编辑:我找到了一个很好的教程,我实际上可以关闭这个问题,除非有人想回答.http://www.androidcompetencycenter.com/2009/01/basics-of-android-part-iii-android-services/

我需要Realm在android 中的数据库中添加自动增量键字段.我怎样才能做到这一点？这可能吗？

提前致谢.

我有一个UITableView有12行的静态和11行,我知道高度需要是多少.

我有一个UILabel,它有动态文本,位于12行内,我如何根据UILabel中的文本制作一个单元格的动态高度.

我在里面尝试了下面的代码viewDidLoad,但它没有用.行保持相同的高度.我还设置线= 0为UILabel

    tableView.estimatedRowHeight = 100.0
    tableView.rowHeight = UITableViewAutomaticDimension

有时我们需要在代码运行之前延迟它.

这是可以通过Handler.postDelayed(Runnable)或CountdownTimer.

哪一个在性能方面更好？

请参阅下面的示例代码

处理器

        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                 //DO SOMETHING
            }
        }, 1000);

倒计时器

        new CountDownTimer(1000, 1000) {
            public void onFinish() {
                 //DO SOMETHING
            }
            public void onTick(long millisUntilFinished) {}
        }.start();