android TextView 容纳不下内容，让字向左滚动的办法

就是大家叫的跑马灯效果。对4.0以上，简单地在TextView里面加上4句就可以了：

android:ellipsize="marquee"android:focusable="true"android:focusableInTouchMode="true"android:singleLine="true"

但是如果这个TextView属于ListView的子View，并且list item设置了android:descendantFocusability="blocksDescendants"等比较复杂的情况时，上述方法不行。必须在自定义View上drawText，在http://gundumw100.iteye.com/blog/965366的基础上，整理了些干货：

FloatableTextView.java:

package com.example.floatabletextview;import android.content.Context;import android.graphics.Canvas;import android.os.Parcel;import android.os.Parcelable;import android.util.AttributeSet;import android.view.View;import android.view.View.OnClickListener;import android.widget.TextView;/** * 单行TextView，容纳不下就左移 */public class FloatableTextView extends TextView implements OnClickListener {    public boolean mIsFloating = false; //是否开始滚动    private float mSpeed = 0.5f;    private float mStep = 0f;    private String mStr = ""; //文本内容    private float mTextLength = 0f; //文本长度    private float mViewWidth = 0f;    private float mY = 0f; //文字的纵坐标    public FloatableTextView(Context context) {        super(context);        initView();    }    public FloatableTextView(Context context, AttributeSet attrs) {        super(context, attrs);        initView();    }    public FloatableTextView(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        initView();    }    private void initView() {        setOnClickListener(this);    }    public void init(String str, float speed, float width) {        setText(str);        mSpeed = speed;        mStr = getText().toString();        mTextLength = getPaint().measureText(mStr);        mViewWidth = width;        mStep = mTextLength + mViewWidth;        mY = getTextSize() + getPaddingTop();        getPaint().setColor(0xff0000ff);    }    @Override    public void onClick(View v) {        if (mIsFloating)            stopFloating();        else            startFloating();    }    @Override    public void onDraw(Canvas canvas) {        canvas.drawText(mStr, 0, mStr.length(), mViewWidth + mTextLength - mStep, mY, getPaint());        if (!mIsFloating)            return;        mStep += mSpeed;        if (mStep > mViewWidth + mTextLength * 2)            mStep = mTextLength;        invalidate();    }    @Override    public void onRestoreInstanceState(Parcelable state) {        if (!(state instanceof SavedState)) {            super.onRestoreInstanceState(state);            return;        }        SavedState savedState = (SavedState) state;        super.onRestoreInstanceState(savedState.getSuperState());        mStep = savedState.mStep;        mIsFloating = savedState.mIsFloating;    }    @Override    public Parcelable onSaveInstanceState() {        Parcelable superState = super.onSaveInstanceState();        SavedState savedState = new SavedState(superState);        savedState.mStep = mStep;        savedState.mIsFloating = mIsFloating;        return savedState;    }    public void setSpeed(float speed) {        mSpeed = speed;    }    public void startFloating() {        mIsFloating = mTextLength > mViewWidth;        // mIsFloating = true;        invalidate();    }    public void stopFloating() {        mIsFloating = false;        invalidate();    }    public static class SavedState extends BaseSavedState {        public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {            @Override            public SavedState createFromParcel(Parcel in) {                return new SavedState(in);            }            public SavedState[] newArray(int size) {                return new SavedState[size];            }                    };        public boolean mIsFloating = false;        public float mStep = 0.0f;        private SavedState(Parcel in) {            super(in);            boolean[] b = new boolean[1];            in.readBooleanArray(b);            mIsFloating = b[0];            mStep = in.readFloat();        }        SavedState(Parcelable superState) {            super(superState);        }        @Override        public void writeToParcel(Parcel out, int flags) {            super.writeToParcel(out, flags);            out.writeBooleanArray(new boolean[] {                mIsFloating            });            out.writeFloat(mStep);        }    }}

MainActivity.java:

package com.example.floatabletextview;import android.app.ListActivity;import android.os.Bundle;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import com.example.zlistmarquee.R;public class MainActivity extends ListActivity {    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);                setListAdapter(new MyAdapter());    }        class MyAdapter extends BaseAdapter {        @Override        public int getCount() {            return 9;        }        @Override        public Object getItem(int position) {            return null;        }        @Override        public long getItemId(int position) {            return 0;        }        @Override        public View getView(int position, View convertView, ViewGroup parent) {            View v = getLayoutInflater().inflate(R.layout.list_item, null);            FloatableTextView floatableTextView = (FloatableTextView) v.findViewById(R.id.floatable_text_view);            floatableTextView.init("速度 岁的 电话 离开 的灯光 撒旦斯蒂芬 无污染", 0.9f, 100);            floatableTextView.startFloating();            return v;        }            }    }

list_item.xml:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="30dp" android:orientation="horizontal" > <LinearLayout android:layout_width="90dp" android:layout_height="fill_parent" android:background="@android:color/holo_green_dark" > </LinearLayout> <com.example.floatabletextview.FloatableTextView android:id="@+id/floatable_text_view" android:layout_width="80dp" android:layout_height="30dp" android:background="@android:color/holo_blue_bright" /> <LinearLayout android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@android:color/holo_green_light" > </LinearLayout></LinearLayout>

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?><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" >    <ListView        android:id="@android:id/list"        android:layout_width="fill_parent"        android:layout_height="wrap_content" >    </ListView></LinearLayout>

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