Android的按钮显示在图形布局，但不是在装置 [英] Android Button shows in graphical layout but not on device

问题描述

我一直在试图对Android应用程序显示两个按钮。但是，按钮不可见，整个页面是一个空白。这是我的XML code -

 ＆LT; LinearLayout中的xmlns：机器人=htt​​p://schemas.android.com/apk/res/android
    的xmlns：工具=htt​​p://schemas.android.com/tool​​s
    机器人：layout_width =match_parent
    机器人：layout_height =match_parent
    机器人：方向=垂直
    机器人：paddingBottom会=@扪/ activity_vertical_margin
    机器人：paddingLeft =@扪/ activity_horizo​​ntal_margin
    机器人：paddingRight =@扪/ activity_horizo​​ntal_margin
    机器人：paddingTop =@扪/ activity_vertical_margin
    工具：上下文=$ com.example.cameracapture.MainActivity PlaceholderFragment＆GT;    ＆LT;按钮
        机器人：ID =@ + ID /捕获
        机器人：layout_width =match_parent
        机器人：layout_height =WRAP_CONTENT
        安卓的onClick =捕捉
        机器人：文字=@字符串/捕获/＆GT;
    ＆LT;按钮
        机器人：ID =@ + ID /上传
        机器人：layout_width =match_parent
        机器人：layout_height =WRAP_CONTENT
        安卓的onClick =上传
        机器人：文字=@字符串/上传/＆GT;
    ＆LT; ImageView的
        机器人：ID =@ + ID /显示器
        机器人：layout_width =match_parent
        机器人：layout_height =WRAP_CONTENT
        机器人：contentDescription =@字符串/上传/＆GT;＆LT; / LinearLayout中＆GT;
 

当我查看图形布局上面code，它显示了完美的按钮。所以，我想这意味着它不是 match_parent 的问题或 WRAP_CONTENT 。我甚至尝试，看看是否引入文本视图会有所作为。再次，它显示了在图形化布局完美，但我的设备上，只有一个空白屏幕是可见的。
难道是我的设备的问题，而不是code？

P.S。我使用的设备是摩托罗拉摩托G，其中有一块4.5英寸显示屏。

编辑：XML文件被命名为fragment_main。这里是我的JAVA code。
    包com.example.cameracapture;

 进口的java.io.File;
进口android.support.v7.app.ActionBarActivity;
进口android.content.Intent;
进口android.graphics.Bitmap;
进口android.graphics.BitmapFactory;
进口android.net.Uri;
进口android.os.Bundle;
进口android.os.Environment;
进口android.view.LayoutInflater;
进口android.view.View;
进口android.widget.ImageView;
进口android.widget.Toast;
进口android.provider.MediaStore;公共类MainActivity扩展ActionBarActivity {    私有静态最终诠释CAPTURE_IMAGE_ACTIVITY_REQUEST_ code = 100;@覆盖
公共无效的onCreate（捆绑savedInstanceState）{
    super.onCreate（savedInstanceState）;
    的setContentView（R.layout.activity_main）;
}    公共无效捕获（查看视图）{        //创建意图拍照和控制返回给调用应用程序
        意向意图=新意图（MediaStore.ACTION_IM​​AGE_CAPTURE）;
        文件imagesFolder =新的文件（Environment.getExternalStorageDirectory（），DCIM /相机）;
        imagesFolder.mkdirs（）;
        文件图像=新的文件（imagesFolderimage_001.jpg）;
        乌里uriSavedImage = Uri.fromFile（图像）; //创建一个文件保存图像
        intent.putExtra（MediaStore.EXTRA_OUTPUT，uriSavedImage）; //设置图像文件名        //启动图像拍摄意图
        startActivityForResult（意向，CAPTURE_IMAGE_ACTIVITY_REQUEST_ code）;
    }    公共无效上传（查看视图）{        字符串路径= Environment.getExternalStorageDirectory（）+/DCIM/Camera/image_001.jpg
        文件imgFile =新的文件（路径）;
        如果（imgFile.exists（））
    {
            位图MYBITMAP = BitmapFactory.de codeFILE（imgFile.getAbsolutePath（））;
            ImageView的MYIMAGE =（ImageView的）findViewById（R.id.Display）;
            myImage.setImageBitmap（MYBITMAP）;
    }
        其他
            Toast.makeText（view.getContext（），没有形象是preSENT'，Toast.LENGTH_SHORT）.show（）;
    }
}
 

解决方案

从未被使用XML文件。

的的setContentView（）为您的活动包含 activity_main 。

检查您的布局 activity_main - 里面设置一个按钮，运行code，因为它是，你会看到按钮

。

你想要的是设置 fragment_main 。

做到这一点的方法之一是：

 公共类MainActivity扩展活动//或ActionBarActivity  - 考虑它扩展了活动
{
@覆盖
保护无效的onCreate（捆绑savedInstanceState）
{
super.onCreate（savedInstanceState）;
的setContentView（R.layout.activity_main）;如果（savedInstanceState == NULL）
{
getFragmentManager（）调用BeginTransaction（）
。新增（R.id.container，新PlaceholderFragment（））提交（）。
}
}公共静态类PlaceholderFragment扩展片段
{公共PlaceholderFragment（）
{
}@覆盖
公共查看onCreateView（LayoutInflater充气器，容器的ViewGroup，
捆绑savedInstanceState）
{
查看rootView = inflater.inflate（R.layout.fragment_main，集装箱，
FALSE）; //这里是你的片段布局
返回rootView;
}
}
}
 

REF进一步：结果
1. 例如：样品的默认结果
2. 多窗格发展：片段结果
3. 如何使用碎片工作 - 安卓

I have been trying to display two buttons on an Android app. However, the buttons are not visible and the whole page is a blank. This is my XML code-

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.cameracapture.MainActivity$PlaceholderFragment" >

    <Button
        android:id="@+id/Capture"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="Capture"
        android:text="@string/capture" />
    <Button
        android:id="@+id/Upload"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="Upload"
        android:text="@string/upload" />
    <ImageView 
        android:id="@+id/Display"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:contentDescription="@string/upload"/>

</LinearLayout>

When I view the above code in the Graphical Layout, it shows the buttons perfectly. So, I guess that means it's not an issue of match_parent or wrap_content. I even tried to see if introducing a text view would make a difference. Again, it showed up on the Graphical Layout perfectly but on my device, only a blank screen is visible. Could it be a problem of my device, instead of the code?

P.S. The device I am using is Motorola Moto G, which has a 4.5 inches display.

EDIT: the XML file is named fragment_main. Here's my JAVA code. package com.example.cameracapture;

import java.io.File;
import android.support.v7.app.ActionBarActivity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;
import android.provider.MediaStore;

public class MainActivity extends ActionBarActivity {

    private static final int CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE = 100;

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

    public void Capture(View view){

        // create Intent to take a picture and return control to the calling application
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        File imagesFolder = new File(Environment.getExternalStorageDirectory(), "DCIM/Camera");
        imagesFolder.mkdirs();
        File image = new File(imagesFolder, "image_001.jpg");
        Uri uriSavedImage = Uri.fromFile(image);// create a file to save the image
        intent.putExtra(MediaStore.EXTRA_OUTPUT, uriSavedImage); // set the image file name

        // start the image capture Intent
        startActivityForResult(intent, CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);
    }

    public void Upload(View view){

        String path = Environment.getExternalStorageDirectory()+ "/DCIM/Camera/image_001.jpg"; 
        File imgFile = new File(path);
        if(imgFile.exists())
    {
            Bitmap myBitmap = BitmapFactory.decodeFile(imgFile.getAbsolutePath());                  
            ImageView myImage = (ImageView) findViewById(R.id.Display);
            myImage.setImageBitmap(myBitmap);
    }
        else                    
            Toast.makeText(view.getContext(),"no IMAGE IS PRESENT'",Toast.LENGTH_SHORT).show();


    }


}

解决方案

Your xml file is never being used.

The setContentView() for your activity contains activity_main.

Check your layout activity_main - set a button inside and run the code as it is, you will see that button.

What you want is to set fragment_main.

One way to do it is:

public class MainActivity extends Activity //or ActionBarActivity--considering it extends activity
{
        @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        if (savedInstanceState == null) 
        {
            getFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }
 
        public static class PlaceholderFragment extends Fragment 
    {
 
        public PlaceholderFragment() 
        {
        }
 
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) 
        {
            View rootView = inflater.inflate(R.layout.fragment_main, container,
                    false);//here is your fragment layout 
            return rootView;
        }
    }
}

Further ref:
1. Example: sample default
2. Multi pane development: fragments
3. How to work with fragments - android

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