如何从自定义视图的类中更改文本视图
Posted
技术标签:
【中文标题】如何从自定义视图的类中更改文本视图【英文标题】：How to change a textview from a custom view's class 【发布时间】：2016-02-05 13:54:02 【问题描述】：假设我在 Activity 中有一个自定义视图，并且在该自定义视图下方有一个 TextView。单击自定义视图后，我想更改TextView 的文本，但是当我使用findViewById() 时，我似乎得到了一个空指针，那么我该怎么做呢？
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_
android:layout_
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.yuvaleliav1gmail.quoridor_ye.MainActivity"
android:background="#dd7d23">
<com.yuvaleliav1gmail.quoridor_ye.ComBoardView
android:layout_
android:layout_
android:id="@+id/bview"
android:background="@drawable/game_board"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<RadioGroup
android:layout_
android:layout_
android:id="@+id/radioGroup"
android:layout_below="@+id/bview"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true">
<RadioButton
android:layout_
android:layout_
android:text="Move Pawn"
android:id="@+id/radioPawn"
android:checked="true"
android:onClick="radioButtonClick"/>
<RadioButton
android:layout_
android:layout_
android:text="Set VERTICAL Wall"
android:id="@+id/verticalRdio"
android:checked="false"
android:onClick="radioButtonClick"/>
<RadioButton
android:layout_
android:layout_
android:text="Set HORIZONTAL Wall"
android:id="@+id/horizontalRdio"
android:checked="false"
android:onClick="radioButtonClick"/>
</RadioGroup>
<TextView
android:layout_
android:layout_
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Your turn"
android:id="@+id/turnText34"
android:layout_gravity="center_horizontal"
android:layout_below="@+id/radioGroup"
android:layout_alignLeft="@+id/bview"
android:layout_alignStart="@+id/bview" />
<TextView
android:layout_
android:layout_
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Your walls left: "
android:id="@+id/yourWallsText"
android:layout_gravity="center_horizontal"
android:layout_below="@+id/turnText34"
android:layout_alignLeft="@+id/turnText34"
android:layout_alignStart="@+id/turnText34" />
<TextView
android:layout_
android:layout_
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="10"
android:id="@+id/yourNumText"
android:layout_gravity="center_horizontal"
android:layout_alignTop="@+id/yourWallsText"
android:layout_toRightOf="@+id/yourWallsText"
android:layout_toEndOf="@+id/yourWallsText" />
<TextView
android:layout_
android:layout_
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Opponent's walls left:"
android:id="@+id/opWallsText"
android:layout_gravity="center_horizontal"
android:layout_below="@+id/yourWallsText"
android:layout_alignLeft="@+id/yourWallsText"
android:layout_alignStart="@+id/yourWallsText" />
<TextView
android:layout_
android:layout_
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="10"
android:id="@+id/opNumText"
android:layout_gravity="center_horizontal"
android:layout_alignTop="@+id/opWallsText"
android:layout_toRightOf="@+id/opWallsText"
android:layout_toEndOf="@+id/opWallsText" />
</RelativeLayout>
comBoardView 是自定义视图的类
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.os.CountDownTimer;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.TextView;
import android.widget.Toast;
public class ComBoardView extends View
private static final int ROWS = 9;
private static final int COLUMNS = 9;
public static Context con;
Paint paint;
GameService game;
TextView turns;
public static Point size = new Point();
/*
* constructor
*/
public ComBoardView(Context context, AttributeSet attrs)
super(context, attrs);
con = context;
paint = new Paint();
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();
display.getSize(size);
turns = (TextView) findViewById(R.id.turnText34);
/*
*/
public boolean onTouchEvent( MotionEvent event )
game = GameService.getInstance();
int x = (int)event.getX() / 100;
int y = (int)event.getY() / 100;
if ( event.getAction() != MotionEvent.ACTION_UP )
return true;
if(game.movePawn)
if(game.turn % 2 == 0)
if(game.isLegalMove(game.ai.MyLocation , y * ROWS + x))
game.board.ClrPlayer(game.ai);
game.ai.MyLocation = y * ROWS + x;
game.board.SetPlayer(game.ai);
if(turns != null)
turns.setText("white's turn");
game.turn++;
else
if(game.isLegalMove(game.player.MyLocation , y * ROWS + x))
game.board.ClrPlayer(game.player);
game.player.MyLocation = y * ROWS + x;
game.board.SetPlayer(game.player);
if(turns != null)
turns.setText("black's turn");
game.turn++;
else
if(((int)event.getX() % 100) < 50) x--;
if(((int)event.getY() % 100) < 50) y--;
if(game.setHWall)
game.board.SetHWall(y,x);
game.turn++;
else
game.board.SetVWall(y,x);
game.turn++;
return true;
public void RestartTimer()
new CountDownTimer(3500, 1000)
public void onTick(long millisUntilFinished)
final Toast toast = Toast.makeText(con, "restarting in: " + millisUntilFinished / 1000, Toast.LENGTH_LONG);
toast.show();
new Handler().postDelayed(new Runnable()
@Override
public void run()
toast.cancel();
, 1000);
public void onFinish()
.start();
protected void onDraw(Canvas canvas)
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);
GameService.getInstance().onDraw(canvas, paint);
游戏是活动的类
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.RadioButton;
import java.util.Timer;
public class Game extends AppCompatActivity
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game);
Timer timer = new Timer();
GameUpdateTimer ut = new GameUpdateTimer();
ut.boardView = (ComBoardView)this.findViewById(R.id.bview);
timer.schedule(ut, 200, 200);
RadioButton pawn = (RadioButton)findViewById(R.id.radioPawn);
RadioButton hWall = (RadioButton)findViewById(R.id.horizontalRdio);
RadioButton vWall = (RadioButton)findViewById(R.id.verticalRdio);
final GameService g = GameService.getInstance();
pawn.setOnClickListener(new View.OnClickListener()
public void onClick(View v)
g.movePawn = true;
g.setHWall = false;
);
hWall.setOnClickListener(new View.OnClickListener()
public void onClick(View v)
g.movePawn = false;
g.setHWall = true;
);
vWall.setOnClickListener(new View.OnClickListener()
public void onClick(View v)
g.movePawn = false;
g.setHWall = false;
);
【问题讨论】：
请输入一些代码！ 向我们展示您的代码、布局和 logcat。 我不知道 lotcat 是什么或在哪里）：，这个想法是创建一个 Quoridor 游戏。它只是我无法真正解决的自定义视图和文本视图的问题，所以我认为只是解释一切都会起作用，因为很多代码与问题无关.. 【参考方案1】：你不能从你的自定义视图中调用turns = (TextView) findViewById(R.id.turnText34);，它总是会返回Null，因为TextView存在于活动xml中而不是ComBoardView中。
您可以做的是在活动中实例化您的TextView，然后将clickListener 添加到您的ComBoardView。
TextView turns;
@Override
protected void onCreate(Bundle savedInstanceState)
//...
turns = (TextView) findViewById(R.id.turnText34);
ut.boardView.setOnClickListener(new View.OnClickListener()
public void onClick(View v)
turns.setText("ComBoardView was clicked!");
);
//...
【讨论】：
好的.. 我知道这是如何工作的，但正如您在 comboardview 中看到的那样，有一个名为 OnTouchEvent 的函数，它检查玩家的某个移动女仆是否合法以及该移动，我需要根据正在更改的文本来更改文本（否则它只会不断更改回合而不管玩家是否玩了回合） 你可以在activity中为你的ComBoardView添加一个OnTouchListener，来处理触摸事件。否则，创建一个包含 TextView 的自定义视图，并像第一次那样在自定义类中管理您的 TextView。以上是关于如何从自定义视图的类中更改文本视图的主要内容，如果未能解决你的问题，请参考以下文章